Doesnt let me to choose paypal balance only the verified credit card?
Weird. When I used virwox, they allowed me to use my paypal balance without any issues. Are you sure that you just don't know how to select to pay with your credit card?
From memory, you do need to have a linked bank account in order to use their services, because they require your account to be verified to buy bitcoin from them. Are you sure that your paypal account is currently verified?
If you can't get it to work, then try contacting support. I don't think anyone here has enough experience dealing with Virwox apart from 1-2 times to answer your questions.