@ZGjim- If this is not a cache problem, you will need to reach out to to PM to have a support rep investigate and correct the problem (and give you a refund/credit for the previous month(s)).
I had noticed that on my account also. The total used/left for the month (I am on the 250MB plan also) never matches the details in history. I always looks like I used more than I did. I had opened a ticket with support (about 4 or 5 months ago), ...
@fixin1 - just the msg saying welcome to US. You can get a roaming pkg for xxxx. That might have triggered as we were flying out of Montreal. Nothing about Mexico.