MTN false advertising and billing

My wife done at upgrade in January this year on a special from the MTN book. The advertised price was R379 for a samsung galaxy A20s. The contract was signed. When the debit orders started going off MTN debited R459.00. We have been querying the store where we upgraded and MTN directly and they insist we signed the contract for R459 so the issue is resolved. The store consultant was also not aware that the contract showed a different price to the advertised price. MTN please note that this relates to false advertising and we will be seeking legal advice as well as taking this matter to ICASA.