Hi, are you currently in the UK or abroad?
Can you see your remaining minutes when you dial *100*7# ?
Occasionally, you'll hear a not enough credit message when calling a standard uk number
Its usually resolved by switching your phone off and on
Call the number in the country code format
For instance if it starts 07732
If it starts 01302
If you still hear a not enough credit message
Post the first 6 digits of a number you can't call