https://en.wikipedia.org/wiki/Painless_Parker
He legally changed his first name to “Painless” when he was accused of breaking a false advertisement law by claiming that his dentistry was truly painless.[1][2] When business thrived, he hired assistants and established a chain dentistry business.[2] In the end, Parker ran 28 West Coast dental offices, employing over 70 dentists, and grossing $3 million per year.
What you would like to have is not paying your ISP for the landline anymore right?
This is easily done by buying a SIP phone (used Yealink T30 start at 15€) and register a virtual number at a SIP provider local to you (e.g. https://sip.us/ starting at 1€/month). Just connect your phone to your regular network, they will give you a set of parameters to configure into your phone and it will behave like a regular landline after that.