Inaccurate account information

for over 2 years my dad has been getting post mails stating that he hasn't made payments but payments are made through a deposit on a monthly basis. He then went to Hollard to complain he was told this miscommunication will be fixed ,but it www fixed for only 2 months and now the post has started all over again of letter stating he hasn't paid when he has and proof of payment has been faxed monthly. Can someone resolve this admin pain