How do I make a formal complaint regarding a seller central case ongoing without resolve for over 2 months?

All of my units of one asin (my own asin) suddently went into 'reserved' and listing became inactive - doesn't seem to be any issue with the units and I'm just getting a copy and paste 'we've passed the concern to another dept'. Meanwhile I've had no sales for over two months for this asin. I've requested many times for a manager to take over the case and requested many times that I want to log a formal complaint but they're just ignoring me every time and sending the same copy and paste response.

Does anyone know how to make a formal complaint in seller central?

Thanks

i would like to ask if anyone knows how to make a formal complaint against Amazon FBA as they have received my stock and my property in UK, and only declared 12 units received out of 36 units, although tracking says delivered we can't get anywhere with Amazon customer service for 3 months now, i have contacted the UK trading standard and they believe Amazon are in a breach of contract with me as they have received my property to their warehouse but refused to return it back to me or reimburse me, i need to raise a complaint so i can go to the financial ombudsman in UK.

I have sent all invoices for the goods but still nothing happening.

yes they said they are going to file a formal complaint