lawyer like letter for release of my funds

i have been selling on amazon for 2 months and they have suspended my account. They have hlled the money for 6 months and i have emailed them to release the balance in my account. I feel that they will only respond to an official lawyer like letter, as my emails are not being responded to. The official time to hold funds is 90 days. Mine has been held for over 6 months. I can provide details of sales and other figures if needed