Invoice nightmare-Telkom

When i went to telkom in Rosebank on the 19th of December to ask them to deactivate my phone cause i reported it ****** a consultant there said to me i should cancel the contract and take a new one and I'll only pay R47 monthly for the previous one cause the value of the phone is too little at the moment so because i obviously don't work there i don't know how they operate.. To my surprise in Jan they debited R722. 68 i thought it's okay cause i had a prorata to pay for dec but then again this month they invoiced me an amount of R595 when i called to ask why they informed me that there's a device obligation for the previous phone.. Question is why upgrade if you'll still pay for the previous phone and i need was never informed that it'll be R141 monthly the guy said it'll be R47 plus my new contract which is R249. 00 they never resolved my query they kept on telling me to go to the branch again to lodge a complaint.. But when i reversed my money they were so rude to call me with an automated whatever they call it to demand me to pay within the next 48 hours or else I'll leave them with no choice but to hand me over and list me to credit bureau.. My question is I've been loyal for 18 months but when i have such a problem no one helps!