If you have successfully opened a store, your member ID will have a door icon next to it (here in the forum, as well as on your feedback / listing pages). It sounds like you changed your member account to a business account, which can not be changed back to a personal account - I'm not 100% sure of the implications for registering as a business seller, but in the help pages eBay do advise to consult a lawyer etc before registering as a business, so if it is not right for you, you may be better off with a different account.
In regards to the phone number, you should have a phone number on file with eBay when you registered your personal details, so it may be that you need to confirm the verification request and it will be conducted via the number already on file.
However, to open a store, you need to have a valid credit (or debit) card on file (you can do this by adding it to the automatic payment options for fees - once the card is on file, you can change your payment method if you do not want them to be deducted from the card), and then go to My eBay > Account > Manage subscriptions, and it will take you through the process of opening a store.
