Hi Rajiv,
Please find my response as follows-
(a) I guess you are using a separate pair of main/sub tr. for posting the Surcharge credit.Now if you want that to show that in the Payment list, you need to configure that as a payment in the SPRO Node. IMG-->Financial Accounting-->Contract Accounts Receivable and Payable-->Basic Functions-->Postings and Documents-->Document-->Maintain Document Assignments-->Maintain Sub-Transactions.
Check the Payment column against the pair of main/sub tr. used for posting the surcharge Credit.
(b) With the second issue, that you are having, you can post the return lot with Enhanced returns tick and type of posting as '2-New Receivables, derived from payment'.
Hope it helps...
Thanks,
Amlan