When should you replace a toilet bowl?

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I had a clogged toilet and I believe my landlord tried to get money out of me for a job that was not neccessary. My toilet has been stopping up off and on for several months and it finally just would not flush. My landlord called somebody in that was not a professional and removed my toilet because neither of them wanted to stick their hand in the toilet to see if there was something in their. Could you please give me some reasons for actually needing to replace a toilet because i have had toilet problems before and replacing the toilet was never an option.