I think if we accept that market concentration for essential services cannot alawys be avoided, there must be an obligation for these companies to provide those services to everyone.
The difficult part is how to guarantee this right without opening the floodgates for all sorts of scammers and organised criminals.
We need some sort of due process proportional in cost to the effects of account terminations (or rejections) on people's lives.
Isn't this how utilities are regulated?