I have a PAYG sim in a mobile phone that I use very rarely, with a small credit balance. I check it now and then to make sure it is still active. When I checked it last night, a recorded message said I could not make outbound calls from the phone and should contact customer service. When I dial my number from another phone it says the number is temporarily unavailable.
I have called customer service but they WILL NOT help me. They repeatedly ask for a password - which I never set up for the account, as it has never been registered online. They are not prepared to listen or try any other way to help me.
Sorry to hear of the problems with your Pay As You Go SIM and account, we appreciate you raising this with us via the forums and welcome to the community.
As enlli has advised we are in the process of removing all Pay As You Go accounts by early 2022, from what you have described it would also be difficult to pass account security if the number has never been registered.
Depending on the credit balance and the number you're trying to call, this may prevent you from making calls. You should however still be able to receive calls regardless of the credit balance on the account. If sounds as though you don't use this SIM card much or at all really so it may not be possible to know how long this has been the case.
The Terms and Conditions can be found here for mobile accounts and Pay As You Go and explain the usage requirements.