What do you mean by completely mobile? You can't access your account via web browser?
Or is it they locked your account and now they want you to only access using their app. If so, What is the need of a phone number? Is it for verification like they'll send a code and you'll enter it? If it is, you can hire someone for that (here on forum). Furthermore, Are you sure they're not asking for a past phone number (If you had any)?
For the app access, you can just use an android simulator.
You can't log into the web browser version without getting the 6 digit verification code from the app on the phone. They've gone completely app-based so that even if you do log into your account in the web browser with the phone number and 6 digit code, there are functions such as sending btc that will only happen on the phone.
I installed an android simulator on my pc thinking that would let me in, but nope, they want a phone number to go with it. It isn't a past number, no, this is all new since the Fall. I haven't been able to log in since August 2017. I have to associate a mobile phone number now with my account and they won't accept my textnow phone number.
I don't have enough btc in the account to justify hiring someone unfortunately, otherwise that could be an option. Although because they have to log into my account with my credentials and their phone number, it's a huge trust issue to do that!