MTN is the Devil

I swear MTN is the devil himself. I had a 24 month contract for fixed LTE I paid R312pm. I never missed a single payment and always paid on time. My contract ended in February 2024 I contacted them to cancel my contract to my surprised they had a long story to cancel my contract then all of a sudden the amount increased from R312pm to R800pm and stopped the debit order on my Banking app. I kept emailing them and calling them to cancel my cantract they never did I no longer use the Contract sim but they keep sending me invoices and as of today I owe them R5263. I regret the day I took out a contract with MTN and I will not pay that money I will rather take them to court.