The first repayment is from the month after the disbursement the loan. Similar to processing charges, you can also try to get this fees reduced. However, prepayment can be done only in full not in part. The company charges the customer cheque bounce charge, which is usually Rs.200-300 each time the cheque bounces. You can change your PDCs but you will have to give new PDCs with an application to the lender who will then return your earlier PDCs.
Some banks offer enhancement of the loan amount after they have repaid part of their principal.
You can go in for a higher loan amount as per your new eligibilty. Moreover, you can get a preferential pricing on your new loan amount. No, it is not at all necessary that you have an account with the bank, but some companies do give a discount if you are already their customer. Companies ask for cheques of local-bank. You can either go to a bank or to finance company and get the application form and information of schemes and formalities, or you can call them and they usually send their agent to your house.