HDFC Bank — hdfc loan cheques getting bounced unnecessarily and penalizing me for that

Address:

GREEN VALLEY HEIGHTS, 140603

This has been a very weird experience with hdfc ltd that i have submitted post dated cheques for my home loan and they are bounced stating that drawer's signature mismatched. With the same sort of signature my cheques are passed last month by hdfc itself. My query is very simple. Why such thing is happening? Either all the cheques should reject or all should pass. What or who decides to pass or reject the cheque?
I have reported it long days back but i am not getting any feedback from your helpdesk. Hdfc is just bluffing the customers with very poor services. It is killing my official hours unnecessarily. Overall i need to take extra stress for this # created by hdfc. I have amount in my account. Why this cannot be done seemlessly without any hazzles?
Last emi i paid somehow by link in which in need to pay extra amount for which i am not responsible at all. I need that refund from hdfc at any cost and request to streamline my upcoming transactions whether it is cheque based or automatic debit.