U-Haul Overcharged me with no justification Toronto, Ontario

So I returned the truck to U-Haul, and originally the retards working at the location couldn't read my contract and insisted on overcharging me. The contract read 333 Miles, but the trucks odometer was in kilometers. As such, they thought I went over my allowed miles. But I did not. They told me that the manager, who was not available would take care of it. A few weeks later, I get an email with an invoice for the extra charge by the jackasses. I called the manager of the location and he said he would take care of it, but no call returned, and every time I call he is not there. I called the corporate office and they said all they can do is file a refund file, and hope for the best. I called the regional managers office and they just said that the individual location is the one who takes care of it.

No refund yet, and they are avoiding refunding my money at all costs. I am willing to sue this company on principle, because they should not be allowed to screw customers over, because of uneducated employees who don't know how to read a contract!