Delays in refunds

Avis car rental is the worst car rental ever when comes to refund of deposit made. I returned the rental car on the 1st of Oct 2018. I kept calling to check when are they making payment and they kept saying 4 days. even On the 14th I was told that the money will be in my account in 3 days. today is the 19th of Oct 2018, I am told that it will be in by Wednesday the 21st.

How can a refund takes over 21 days from a company like AVIS? bad bad service