how to write a letter against refund of payment, actually i pay excess payment (actualy amt 1021 but pay rs 2052) but now i take refund of balance amount
Your question is unclear. Also, you are not asking about an English language question but instead asking for help with phrasing a business letter.
I recommend that you ask a friend who speaks both your native language and English fluently to help you with this as it is a matter of money and you should make sure to express yourself clearly.
However, if I understand you correctly and you simply wish to demand a refund of the balance of 2052(amount paid)-1021(amount of the bill)=1031(amount you are owed as a refund), the following would work:
"I paid 2052 and the amount of the bill was 1021, therefore I have overpaid.
Please refund the balance owed to me of 1031. Thank you."
I still recommend getting someone truly bilingual to help you with this.