Billing Issue.

Extremely frustrated, with MTN billing: Because of an error done by Mondo they charged me an early upgrade fee, which MTN then credited to me at the end of November 2022, however at the end of December MTN debited R3441.72 from my account which is incorrect. as my monthly bill is only R2397. My Debicheck limit is R3000 which MTN has not adhered to. I need them to assist in crediting my account with the difference which is R1044.72. I have sent multiple emails and communication and get totally ignored.