You can if you have admission to another school. So submit LOA through webform. If processed with current school then you cannot change it. Sometimes people send a webform with new LOA and school but in the meantime, get approved for original school. Then they have to a) apply for a new study permit or b) come to Canada and study at school on permit for a semester and then change schools. If changing make sure it is an equivalent program.
What type of degree are you applying for and when were you planning on starting? There is no point in coming to Canada until you get admission and study permit to attend the better school. Unless you are willing to attend a whole semester at the other school and then transfer. Too many people were changing schools and programs when arriving in Canada (typically to much easier programs) so the rules changes a few years ago.
I'm willing to change my university before coming to Canada so that everyone is sorted
If if gets approved with your current school, you cannot change it. You will need to apply for a new study permit. That is why if your application has been in process for a few months, you need new LOA ASAP.
