Nedbank taking their payments but claiming it hasn't been paid

I am paying off a loan with Nedbank. They take their payment on the 15th every month. Since lockdown began they continuously SMS me telling to contact them regarding my payment not being received. Yet, the money has been deducted from my account. Last month they apologised profusely and said it was a mistake and it won't happen again. This month they are doing the same thing. Why do I need to use my airtime to tell them they have made a mistake?