Very very Dissapointed

I am disappointed I am lon standing client of MTN and signed a new contract in January 2019, paying R1668 for 24 months but since November 2019 I am now paying R1894 and I went to MTN office in Pavillion when I recieved my statement to query- Owen told me it was sorted and it would credited then December 2019 came same amount no credit. I went back to MTN to Owen again to find out oh no credit not sorted problem not sorted and I must get signed copy of contract from The MTN store I upgraded at. Why dont MTN have the contract already and why is my problem i signed 24 months at R1668. The problem is still not sorted and I am the only one following up. Come MTN please can some one who can actually help phone me.