Careful. Sometimes they do systemwide audits of accounts and catch these and when you don't even realize it (because no one reads the notices in their bills), your account gets that $100 reversed. I say it now because it could take a few cycles to hit. I've seen it happen before at both Sprint and Verizon while there.
Just don't be surprised if it does. If not, then keep your trap shut and hope you stay under the radar.