iPhone SE receipt.

I need to see if there is a way to get a purchase receipt from Xfinity Mobile. I’ve tried countless times to get one at the store but they just tell me they don’t do purchase receipts but just the emailed purchase summaries. I’m trying to get Apple to remove my uncles activation lock as he and my cousin forgot his Apple ID password and recovery phone associated with my uncles Apple ID. I’ve sent screen shots of my uncles iPhone serial number and the purchase summary with matching IMEI numbers but they won’t accept the screenshots I have and require the original purchase receipt from Xfinity. Any ideas?