Hi Dmitry,
>>My question, does using cell phone number for business "sound" unprofessional?
If in doubt, something like
https://www.receptionhq.com/ gives you a few options to handle landline calls for a lot less than $400/month. Options include a receptionist who can transfer callers to your cellphone or take a message that gets texted to you if you don't pick up.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1