Bad service

My insurance hired on my behalf as curtasy car on the 6 April, a holding fee was paid then the carvwas released to me to use,the car was returned on the 4th May,of which I was told that my balance will update after 7 days,which it has not up until today,I fully understand that the amount taken on the 6th April will not come back as it was meaning full amount cause the outstanding balance for the car usage or charges will come out from that holding balance,I called and spoke to a customer service agent on the 16th May I was told that it will update after 48 hrs,I called my bank on the 19th April and they informed me there was no outstanding instruction to release funds,I called AVIS again on the same day 19th and spoke to Abraham he informed me that he will escalate my request and will call me back the same day,and up until now no call received from AVIS,can someone sort this out,I know it's not a lot of money but it is money that is due to me.