Was there another reason why you thought you would be suspended? Is there anything else that has been flagged on your account to make you feel concerned? Amazon account suspension only happens when you have done something wrong (against terms of service) or if banking details need to queried and changed.
As long as you have a bank account or credit card active to pay for the storage charges you mentioned, there should be no reason for this switch to trigger anything negative.
The move to the professional seller account is a simple one and Sellers move from individual sellers to professional sellers all the time and with ease. You just go from not paying a subscription to paying a monthly subscription to amazon (about USD$39.99 per month).
– Top right of Seller Central dashboard to ‘SETTINGS’
– Select ‘account info’
– Look to your right on the page for ‘Account management’
– Select ‘upgrade account’ (mine is already set to UPGRADE, but yours will hopefully list ‘upgrade account’)
SEE SCREENSHOT below to help you …
Please let us know if there is any other reason behind your concern?