Earlier quoted context omitted.
That's similar to the idea I had for combating texting spam: - If your number is in my address book then texts are free for you - If this is the first time you are contacting me then you pay me $1 There are probably downsides and ways this will screw up real relationships but it will certainly increase the cost of spam.
One issue I can forsee: - Every contractor (plumber etc) you hire will ask you to please add them to your contact list first so that they can message you. - After a while of half their clients not doing that and lots of fees on their end, contractors stop providing a phone number at all, asking you to please install ContractorApp to communicate with them.
contractors can add this to their invoices if they care.