@Uroobaimtiaz are you in a rush to update your credit card or your service will be cut off soon (or already ?)
if not rush, then wait for PM support to reply. Their official respond time is within 72 hours but they usually reply within 1 to 2 hours. Yes, weekend and holiday could be longer
If you waited 4 hours and if you urgently need to get back in, try to open another ticket again.
In the meantime, did you try to use the Forgot Password link ( https://selfserve.publicmobile.ca/forgot-password/ ) and try to put in any email address you have , once a correct email address is entered, it will move to step 2. But the next challenge is to answer the Security question that you have set up yourself before.