overcharge

Short definition from Wiktionary

Verb

1. 1
   To charge (somebody) more money than the correct amount or to surpass a certain limit while charging a bill.
2. 2
   To continue to charge (an electrical device) beyond its capacity.
3. 3
   To charge (someone) with an inflated number or degree of legal charges (for example, charging them with a more serious crime than was committed); to upcharge.
4. 4
   To charge or load too heavily; to burden; to oppress.
5. 5
   To fill too full; to crowd.
6. 6
   To exaggerate.

Noun

1. 1
   An excessive load or burden.
2. 2
   An excessive charge in an account.
3. 3
   Any amount erroneously charged to a customer above the correct price for a product or service.