Can you stop with the harassment

My mother has a loan with African bank which has been taking forever to pay back because of the errors you keep on doing on her account. She has been paying this loan and as a matter of fact she paid on the 22 of Jan however she is being harassed and threatened by African bank. She is getting SMSes that a payment hasn't been made and she will be referred to lawyers. She needs to make payment in 10 days. Can you treat your customers fairly hey.