Amazon and respectively vat charged on sales com

hi all,

I hope you can help, I was a seller on amazon.co.uk ( on their marketplace) Amazon owe me VAT on the sales commission they have charged me for the last 2 years. Amazon confirmed that they would pay back the VAT respectively but 90 days later they changed their mind due to my account having seller performance issues. Essentially as Amazon was treating me as a business to customer supply and as a result they charged by VAT on the commission, however when I entered my VAT number I moved to a Business to Business supply (i have been registered since 2009) and as a result no vat should have been charged on sales commission going forward and retrospectively to which Amazon agreed to.

Anyway Amazon then issued me a series of incorrectly addressed VAT invoices with no credit and stated that I should go to HMRC to claim back the VAT from them. however I am fairly sure this is wrong, why would HMRC credit me the VAT which Amazon has charged me, they have been enriched by VAT incorrectly charged? is it not the responsibility of the customer ie Amazon to refund the vat and internally correct it on their systems so it balances?

please can anyone provide me a link to guidance/notices showing that Amazon is responsible for the credit payment. i don’t want to approach HMRC with incorrect invoices and then on top of that claim a credit which HMRC are not responsible for, I don’t want penalties from bad advice given by Amazon.

thanks