toliet backing up after roter rooter and replaced toliet
Left as an answer because with the information provided I believe you were taken advantage of ( screwed in common terms)
Wow, I would call the bbb and state exactly what you did here. Sounds like a really scum type of business!!!!!!!! Sorry but old toilets have more water and actually clear the piping better,  to tell the truth you should have a case and find a different plumber and get some of your $ back !!!!!!!!