Please stop stresiing me out

Cell C took my phone for repairs and gave me a quote over R2800 payable over two instalments. The first instalment of over R1420 was deducted in January even though they did not fix my phone. In February they rightfuly debited R400 which is my normal instalment for my contract over 24 month . This month they debited R1421 and only God knows why. They failled to repair my device but still debited repair amount in January, took the correct instalment in February and now debiting R1421 in March.....Why? Do you think Im stupid and naive? please reverse that crazy instalment asap cause my account is on a negative balance because of Cell C. I promise you once Im done with my contract I want nothing to do with Cell C and their incompitence. But I need my money rersersed accordingly please.