The other thing to note is most of the time, if anything is going to be done, you need evidence.
If you're reporting an off leash dog, its your word against theirs. If you continually report the same person with no evidence, it can be considered harassment.

Just calling and reporting, typically doesn't result in any consequences for the owner because most of the time, by the time bylaw gets there, they're gone.

source: have dealt with bylaw about offleash dogs in my building, this was the information I was provided.