Product: Credit card

I have been trying for several months to lower my balance by sending checks to Barclay by MAIL to transfer part of my balance to a 0 % offer my mother received from her bank. She has kindly offered to help me with her offer, using it to pay part of my balance at Barclays. TWICE I HAD CHECKS SENT and TWICE, Barclay screwed up and the payment was not made!! I I am writing so I have a written record of my complaint, and I want to receive an answer also IN WRITING from Barclay, indicating EXACTLY WHERE I HAVE TO SEND THE CHECK AND WHEN IT WILL BE CREDITED. 
I am extremely frustrated and will not waste my time on phone calls anymore! I have spent too many hours over many phone calls with Barclay, since XXXX. I have explained it is impossible for me to keep making payments at Barclay 's high interest rates. I have been in and out of the hospital since XX/XX/2023 due to a serious XXXX XXXX. I am trying to transfer some of my high debt at Barclays to my mothers bank so I can keep my credit rating, but it has been ridiculously difficult to consummate a simple balance transfer. What kind of a Bank are you? 
I first had my mother 's bank XXXX XXXX XXXX XXXXXXXX ) {$2000.00} on XX/XX/XXXX. I spoke to a representative and was told the balance transfer could NOT BE MADE ELECTRONICALLY and I had to send a PAPER CHECK to XXXX 's main US office in Delaware. I was surprised that a bona fide, modern bank would not be able to receive electronic payments but in good faith I complied. 
XX/XX/XXXX : My mother asked XXXX XXXX XXXX to send the {$2000.00} check there by mail on XX/XX/XXXX, which they did right away. 
XX/XX/XXXX : I saw the payment had not been made so I figured it the paper check was lost in the mail. My mother asked XXXX XXXX XXXXXXXX to put a stop payment on that check and to issue another check for the amount of {$2000.00}. 
XX/XX/XXXX : I asked where this second check should be sent, since the first check never made it. Barclay gave me a different address in a po box in California. XXXX XXXX XXXX sent the SECOND PAPER CHECK for {$2000.00} by mail to that address. 
XX/XX/XXXX : Seeing the payment was not made by the second check, I again called Barclay. The rep said that was not the right address and offered to give me a DIFFERENT ADDRESS!! That is, place another stop-payment, be charged for it, and then have XXXX XXXX XXXXXXXX send another check by mail!!! I respectfully declined and said I would just wait for it to arrive XX/XX/XXXX : My mother received a letter from her bank saying that Barclays SENT BACK the check, claiming it had the wrong account number!! At this point I figured out that Barclay is playing a dishonest game, trying to avoid transferring my balance there is no other explanation. I called Barclays and they said the check was made out for my bank account at XXXXXXXX XXXX, which is the bank I use to pay Barclay monthly. There is no way my mothers bank made out the check made out a check for that account, because my mother does not have my XXXX account number! So clearly, Barclay is either inept or deliberately messed up the balance transfer. 
I am completely at a loss for words. I am livid that a simple balance transfer has been so difficult. I want to maintain my credit score and am trying very hard to lower my balance at Barclays using an honest balance transfer.