bad reflection on mtn service cotradiction regarding mail.and sms received

one of my contracts has come to an end ofits period . i phoned mtn retensions department to cancel the contract. the lady smooth talked me into renewing the contract for a 12 month petiod. i.agreed. she also sent me a proforma invoice for R1600. thats the value of the contract..in the mail stated that this was not an invoice at all. today i received an sms stating i owe them R1600 to continue. Totally.the opposite of what they told and mailed me.Totally unacceptable and disgusting..shows clearly that one cannot trust mtn and avoid them at all costs. wont be fooled again. they dont know what they are doing.