See page 21 of
http://support.t-mobile.co.uk/resour...S_30.07.12.pdf
You must make a connection action at least once
every 180 days. If you do not, your SIM card will be
disconnected from the network, and you will not be
able to use the service at all. You will also lose your
mobile phone number. Any credit on your account
at the time of disconnection will be forfeited.
‘Connection actions’ are:
– Making a chargeable outbound call
– Sending a text message
– Topping up your account
– Making a payment for a value added service
– Registering your details
– Making/sending or receiving a Family Booster
call, text or picture message
I'm trying to decide if it makes sense to switch to one of the current plans. I joined a few years ago and can't figure out my terms, but so far I don't see any downside to the newer plans. Texting to non-UK seems to cost 20p now, while I just got charged 50p. It turns out I don't get next month free unless I join a new plan before topping up.