Account query with MTN from constance Ratshilima

Hi I apply for mtn contract in july 2021 . My monthly installment is 319 . From August they deducted 319 till November but on the 4th of December they deduct R1791.when go to the branch to query they tell me I over spend which was lie . And they never help me and never return my money .and I decide not to use their sim card anymore. On 5th of January 2022 they deduct the same amount R1791 when i call them they say i over spend i never use mtn sim card their monthly data and min is still the and their telling me i over spend. Now they send me an sms that am owing them R1800 . Please help me