Pure **** on loan agreements

I took the loan of R160 000 in 2018. Last debit date of R4 511.89 was supposed to be February 2023 (Copy of contract available in my possession). The loan was before Covid. My installment were the same throughout the entire period. Repo-rates were dropped to the lowest basis points and I paid the same amount. Now that I am finishing my loan I am told that the bank added 2 more months on my loan amount due to change in the interest rates which were rather dropped in the past 2 years. The bank won't provide me with their re-calculation which weren't communicated. They told me that they sent an sms which I did not receive. I asked for the proof of that sms but it won't be made available. I hereby demand the updated contract with my signature agreeing to the change in number of months. I can't be made liable for over R8000.00 which I did not agree on. Is this perhaps your trick to **** people like they always say?