Jet account that does not decrease

My Mum has an account with JET,the last time she bought with the account was 2023.Untill now yue account does not decrease .When I add all the amounts paid since then it's over R7000. Every month she is paying over R600 everymonth for the passed 3 years . She is 84 sickly and they keep on harassing her demanding her to pay.Why is the account/amount not decreasing. OR there is someone using the account just like when there was someone was buying data with her account while she does not even use data Jet please why are you treating your customers so bad..My mum is very old to be stressed by your agents When is the amount going to decrease and end