OSC | Airtime Buying Guide

At OSC, we offer a broad variety of airtime options for different satellite networks, to ensure that your device can keep you connected when you go off-the-grid. This page aims to answer any questions you may have about Airtime, SIM cards and Airtime networks. We have even included some of your Frequently Asked Questions.

Why do I need Airtime?

Similarly to mobile phone credit airtime enables our device to operate and connects you to others via voice, SMS or data access. Airtime is required for all our Satellite phone, trackers and Internet terminals. Therefore, airtime is not required for our Radios and SOS beacons and these are devices are subscription free.


We are commonly asked about the best airtime option for our customers - should they purchase Prepaid or Pay Monthly Airtime? Our answer always depends on how long the customer is planning on using their device! For short term and low level of usage of the device, we would recommend Pre-Paid plans, as you can easily top-up your device with more airtime.  However, for long-term usage or guaranteed additional airtime each month, pay monthly plans would be most appropriate. 

Pay Monthly airtime, is just like a monthly contract for your mobile phone. Airtime is added to your SIM Card and a direct debit payment is required each month. 

Prepaid airtime is added to your SIM card at activation. Airtime can be added at anytime to top-up the amount of airtime on your device, however it must be noted that airtime has an expiry date. Airtime is only valid for the specified amount of time, for example Thuraya NOVA airtime is valid for 2 years and if there are remaining units, a renewal fee will automatically be taken by the network to keep the SIM active, but the airtime balance will be deducted. An alternative option on other networks is - purchasing validity extensions or adding more airtime to the device. We recommend that you take note of your airtime validity date, as once this has passed all remaining airtime is gone and cannot be claimed back. Find out how to check your balance here.

Airtime Conversion

At OSC, we are frequently asked about how many minutes are required for messages, data or voice calls. A basic guide (uploading/downloading documents will use up for data units that browsing the internet or answering emails) 

Don't forget you need a SIM Card! 

SIM Cards

Similarly to a mobile phone, you need to have a SIM card and credit. Once you have ordered your SIM Card you can add airtime to the number on the SIM Card to ensure your device is operational. SIM Cards are free to order from us, so the only cost is postage if you are outside the UK. So why not buy the device and airtime from us, to share delivery cost? 

Fortunately a SIM card does not expire, unless it is an Iridium SIM card. An Iridium SIM will automatically be deactivated 270 days after the credit expires unless you add a new top-up.  If you want to reactivate the Iridium SIM you will have to pay a reactivation fee. 

If the SIM card is broken or lost, any airtime cannot be transferred once the SIM card has been activated! Therefore, if you have any questions about adding airtime ask us before activating your SIM Card. For example, we often get asked whether you can have a SIM card from one network and the airtime from another, this does not work. If you have an Iridium SIM card you must have Iridium airtime. This is also due to network terms and conditions, therefore you must buy the SIM Card, Airtime and Device from the same satellite network provider. i.e. An Iridium SIM Card, with Iridium Pre-Paid Satellite Phone Airtime for the Iridium 9555. 

Frequently Asked Questions

Does airtime need to be activated or will it be automatically on my device? For a prepaid airtime customer, you are required to go to our activation page https://www.globaltelesat.co.uk/sim-activation once you have received the SIM card.  For pay monthly airtime customers, you are asked to input an activation date on the airtime contract so we can setup the activation of the airtime as part of the contract processing.

Do I get notified when my airtime is running out? Yes - customers can be notified with an automatic email including balance and expiration date information shortly before the airtime expires. Check with us that your email address has been registered for the updates. Upon request we can also send an SMS message to satellite phones in case you have no access to emails due to being out in the field with the device. An additional option to check your airtime balance is to manually check this, at any time on the device. Find out how to check your balance here.

Does the tariff charge differ depending on where I am? Generally call rates are all the same unless you choose specific SIM options or vouchers. For example, a Thuraya NOVA SIM offers customers inside the NOVA zones lower rates than a standard Thuraya SIM. Similarly, if you choose an Iridium regional voucher this will give you preferential rates in certain countries. They are shown on the prepaid top-up page.

How long is airtime validity? The length of airtime validity depends on the network and the airtime plan. All this information is provided on our airtime pages and is confirmed during the purchase process. Additionally, we send reminder emails to let you know when your airtime is coming to the end of it's validity. 

Is the person texting or calling my device charged? Yes. The cost to call a satellite device can be expensive, due to terrestrial networks charges. Therefore we recommend negotiating a time to call someone via message and then the satellite phone holder calling the mobile phone or landline. Alternatively, communicating just by SMS between satellite phone and mobile does not usually cost very much. 

If I only need airtime for emergencies, what is the best plan for me? Once again, this depends on location requirements but generally Thuraya NOVA is the best for emergencies due to the 2 year validity but is dependent on whether you are in the Thuraya coverage area.  Alternatively, we would recommend Inmarsat as this has a better coverage than Thuraya and has cheaper airtime options than Iridium.

Does airtime usage vary if I call a mobile vs a landline? A mobile and landline have the same rate per minute from most satellite phones. However these rates can vary on BGAN etc.

If my airtime runs out can I still call an emergency number? Unfortunately not. Even the SOS button requires airtime by using either data or SMS allowance to send to Search and Rescue operators - therefore running out of airtime is very dangerous, especially in remote locations as a satellite phone without airtime is completely useless! Therefore, we recommend that you check your balance and look out for low balance notifications. Find out how to check your balance here.

If I run out of airtime and need to top up, how do I contact you? You can contact us for airtime top-ups from anywhere in the world. You can call us from the satellite phone, and in the worst case scenario we can do a phone payment in real time. However, we understand that this can be difficult due to signal problems or low airtime, therefore we recommend you assign a contact to top-up your airtime. By providing your details and your SIM card number to a trusted contact, we can top-up your device for you whilst you are off-the-grid.

Satellite Networks Available

  • Iridium is the only satellite network that provides customers with truly global coverage, for you to stay connected anywhere in the world! Plans are available for their Satellite Phones, Satellite Trackers and Satellite Internet. These include the Iridium 9555, Iridium 9575, inReach trackers and Iridium GO!
  • Also, Iridium offers Pre-Paid and Pay Monthly for their devices, excluding inReach trackers which have monthly subscription plans only. 
Contact Us

If your question is not answered, please do not hesitate to contact us via Email, Phone or the Chat window

Email: info@gtc.co.uk

Phone: +44 1202 801290


hours of operation

Monday - Friday
9 AM - 5 PM GMT


Get in touch

UK Enquiries: 0800 112 3919

Int Enquiries: +44 1202 801290

Email: info@gtc.co.uk


find us

Global Telesat Communication Ltd
19-25 Nuffield Road,Poole
Dorset, BH17 ORU, UK

Your cart

Wish Lists