U.S. phone number options while living in another country

I am a solo searcher living in London and I am acquiring a business in the US with my business partner.
We are currently using overseas phone plans to make calls from the UK to the US but we would like
to get a permanent U.S. cell number or alternative that we can use while we are living in London,
without paying ridiculous monthly fees.

We have tried to use the 2nd Line App but the call quality is very poor.
Any suggestions for solutions would be appreciated.