Not happy with MTN

I have 2 data contracts with MTN. Just recently upgraded one of them. Instead of MTN deducting R600 on my account they deduct R1400. Called their call centre and i was told that they didn’t discount my second contract and they will refund me. I have been waiting for 2 weeks still no refund. Just tried calling them and they keep dropping the phone🤬🤬🤬🤬🤬