FBM orders when only FBA

Hi Guys

Please can you help with some advise?
We have been selling on Amazon for over 3 years and in the last couple of weeks Amazon has made some of our products available as fulfilled by merchant. We only sell FBA and have never sold any products FBM and because of this we do not have the facility to fulfil any FBM orders.
We have had to cancel all FBM orders as they come in and this has now meant that we have a massive order cancellation rate and Amazon are threatening to deactivate our account. On top of this they have now blocked our most popular ASIN (both FBA and FBM) when they made it available FBM stating that we have it listed as no stock available yet they are continuing to pass FBM orders through to us on the system.
Has anyone come across this before and have a solution to the issue?
SS has told me to delete the products and re-list, which i have done but they just come back with the same issue.
Thank you in advance for your help.