The best replacement for overage is overfill.

The best alternatives to overage are rated as following:
★★★★★  overfill
★★★  shortage
★  overage

Your alternative for overage is not listed? Suggest!
Speaking about overage, one probably shouldn't forget about coupons.

Other search terms related to overage and their ratings are:
★★★★★ coupons
You have in mind a companion for overage and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of overage in all years. Click on graph for more.
overage
overfill
shortage