My mother had a pay as you go sim - being used only very infrequently, she had topped it up £20 around 3 years ago, had tried to use it several times but seemed unable to, although I could call her on it (which was fine) I rang her a few days ago and it appears they have given her number to someone else as it had not been used in the last 6 months - not even prepared to refund her credit! Won't be using them again!!