When using Pay As You Go (PAYG) SIM cards in equipment such as dialers and gate openers you should be aware that the network may chose to deactivate your SIM card should you not meet the minimum usage requirements. In the UK the strictest networks require at least a call or text message to be sent once per quarter – Lebara Mobile require 1 call/SMS per 3 28 day calendar months.
For details of the terms and conditions for each network I recommend following this link with an excellent article written on the subject:
Further details can be found here on the basis for these policies:
Our GSM equipment has two SIM card Keep Alive functions which automatically send an SMS or dial a number to keep your SIM card within the terms and conditions of the network. All products have the Keep Alive Text feature which sends an automated SMS message at user specified intervals to their chosen number. This is set up as follows:
KAT 07000000000,28. Sends a keep alive message every 28 days to 07000000000
KAC 01512834306,80. Dials 01512834306 every 80 days
Should the call go unanswered it unit will retry 4 times and will then send an SMS to the first master number with the following text ‘KAC@Fail’. In this case a manual call should be made with the following command:
Dial 01512834306. …or the number of your choice
Where your network requires a call to be made but your device has firmware prior to F3.18 we recommend setting the Keep Alive Text message to remind you to make a manual call for your required interval using the dial command. Ensure the call is answered.