Over Billed by MTN

I’m on a contract with MTN for DATA’s and Router. I have been a client since 2016. I have been over billed since May it’s more than double of what I have been paying. Then June got charged way much more than May. I have sent an email to complaints but have had no feedback. I was due for an upgrade end of May, my upgrade was approved early June. I have not been called by consultants to sign or pick up anything. I’m highly frustrated and thinking of canceling my contract. But I would like my money back or atleast some sort of explanation. Ref number given to me when I called the call centre on the 20th of June is: Ref: ***

I hope I get some positive communication after posting this.