ohk, The best thing is to apply for new study permit based on NEW LOA. I don't recommend to travel to Canada with old LOA. As you already sent detail about changing your DLI. The boarder officer might check these details and refuse your entry. They might ban you from RE- Entry Canada for certain years. You are PHD student and have great knowledge and sense of humor.I have a fully-funded scholarship. No tuition fees required.
Before taking any decision , Again just go through updated detail about changing DLI on this link https://www.canada.ca/en/immigration-refugees-citizenship/services/study-canada/change-schools.html
"If your application has been approved
If your application for a study permit has been approved and you change your DLI, you must submit a new study permit application with a new letter of acceptance.
You must also pay all the fees for the new application."
the above quoted lines from official IRCC website and it clearly says that you need to apply for new study permit and pay all new application fees.
GOOD LUCK!!!!