BPTP — Refund

I purchased plot with BPTP and they have taken excess payment (INR 80, 000) from me

I have chased for many years to refund or adjust that excess money for my maintenance charges (transfer from BPTP to BPMS A/c).
I have been to their head office, called few staff, dropped mail to customer care.
In Jan 21 they said they have transferred money to my maintenance a/c (annual maintenance charges appear in BPMS a/c) and i highlighted that it doesn't reflect.
They said it will reflect in a/c by Apr 21.
Now i have received invoice from them to pay annual maintenance charges and no money is transferred.

I see below 2 issues in dealing with them

1) Unfavourable terms for Individual buyer - First of all they kept excess money and didnt pay interest whereas when they ask for payment they put clause of 18% interest charge if paid after due date.
2) Poor response to resolve customer queries / issues - I chased for many year to get excess money refunded to me but till now it doesn't appear to happened.