vodacom *****s from my bank account

Good day. my phone was on prepaid with vodacom via nashua. but since nashua moved all numbers to vodacom sp. my old sim card was converted by vodacom to a contract in error my contract ended in 2008 with vodacom.then in 2011 with nashua. i been on prepaid for 2 years now..now since they converted me to contract without my knowledge...they are also using my bank details from my previous contract to deduct for this account..i have called them several times that i do not use the number anymore. i have given to my niece from 2 years ago. please fix and move back to prepaid and refund all the money incorrectly taken from my account unauthorised.