poor service with entrapment

on 5 Dec 2018 i went into MTN Fairlands wesbank campus and signed up for a 20 gig data 12 month contract to be added to my current contract with them,,, ********** 951..got confirmation that same day that contract was approved..great service..then things fell apart..the sales agent did not put this onto my existing contract instead created a new account..When I told her that I was not going to accepted that, she promised to correct on the 12 Dec...later that day she called me to advise that MTN could only correct this if I changed the contract to a 24 month one...ofcos i refused this.. said to rather cancel the contract..she said she would get back to me...never did..I went out the country on holiday and returned yesterday to find that this issue is still not resolved...Is this a marketing trick by MTN to get 24 month contracts instead of 12 months...thats just *******!!!I now find that I have already been debited for the monthly fee and yet Have had no benefit as yet....IF MTN are not going to add this contract to my existing sim ( ********** 951) then please cancel the contract and refund my funds already paid..