Mtn mobile complaint

Good morning, my name is Anelisa Mvoko from Cape Town. I have a complaint against MTN mobile, on 13 May 2019 I returned back a mifi-router which I DID not even open and use . End of May and June Mtn debited money from my account and I could not reverse it because they were so clever to include it on the contact phone debit that I have with them. Mtn only stopped debiting money end of July and I've been making a follow up with them only to be given different reference numbers all the time and I have been told on different occasions that I should waiting for days and when I contact again I'd be told to waiting again. Last straw was last week 28th August 2019 they told me to wait for 72 hours cuz the billing department is busy sorting out my reimbur*****t and I just called them now and they telling me about waiting 21 days. Mtn is just giving me a run around with regards to paying me back the money they deducted for 2 months and I have been very patient with them. Your assistance in this matter will be highly appreciated.