If I'm understanding you, they are reporting the current balance as what you originally borrowed and not the increased amount that you owe today?
If I'm not mistaken, this might be explained by capitalization. It seems off that it wouldn't, but if none of the interest has capitalized, then the principal would be the same and they would be under no obligation to report more than that. (Although.... Why would you want them to?) What they are reporting would be accurate.
With federal loans they leave it up to the servicers, so I would imagine the private loan lender can tell you how it should report.