Over data

Just Moved In
I have two numbers attached to account, mobile phone and Drive+(Mounted in car).
Dec 26 recv’d message at 90% data used of 1GB. Car which never was used Dec 25 used 67.85Mb on that day,so there would be $13.00 over limit.
Received message Dec 27 saying Drive +had used all data. Same car, that was not used, that data was now 93.88 Mb data for Dec 25
Then received message that being over limit was going to be $20.00 added to account. Tried getting answer at TELUS store as to how data number changes from one day to the next for a car that was not used.
Spoke with customer service by phone, and bth times was not given an answer, so gave up
Jan 4, went to account to find that number has changed again. Now with two phone numbers the total data used has gone to 681.775mb
Three messages from TELUS advising over limit, excess charge pending, two attempts to talk to a person for an answer, and now am no longer over limit.
How can it be possible that TELUS can get this so wrong? How am I expected to be a loyal customer to this type of business?