18333903721 is this legit koodo number?

Did the person say anything about the reason they call?

Spammer can spoof the number as well, so knowing the number doesn’t mean it’s safe. Make sure you didn’t give out personal information that you are not comfortable with.

This is a legit Koodo number,  but as Dinh days, scammers sometimes spoof legit numbers.  If they start asking for personal information that Koodo already has or should have, that would be a red flag.  They also should already know your current plan details.  If they don’t they are scammers.