Bad service from FNB

My dad is an FNB client. On the 30th December 2020, he lost his sim card. Then he went to report in the branch. Then later on the branch called him saying there's an application for a loan under his name. He disputed that saying they mustn't approve anything. He knows nothing about loan. Then, later on, they started debiting money from his account. He went to the branch (Greenstone branch) they said they have stopped everything. But even now the bank is still harassing him about something he doesn't know and he told them from the start that he didn't apply for a loan. Please assist the bank is abusing my dad.