Avis Budget - Deposit refund headache

It seems Avis does not return the car rental deposit to its customers without a fight. It has been 2 months now that our elderly mother is going up and down trying to recover her funds. Unauthorised amounts went off of her account, finance ladies rude on the phone. Official complaint email sent 2 weeks ago, not even a single response.

Unacceptable and down right shameful