I've got tax return 2 times, how can I return one?

Hi all I received tax return in July (X pounds) (after that HMRC has got benefits details from my employer, so I paid some to HMRC (Y pounds)). Now in September I've made a self assessment, and I've got return again (X pounds - Y pounds). How can I return these money back to HMRC and show them their mistake? (I made a call today but spent 45 minutes on line and after several questions from their side they dropped my call) Thank you. Nick.

Hi Nick Mi,

If you received a repayment from both PAYE and Self Assessment we would need to review your record.
Self Assessment: general enquiries

Thank you.