Do you mean one of these?
1) CHOP (Children’s Hospital of Philadelphia) billing/customer-service — information about how to contact CHOP Patient Financial Services, insurance, payments, appeals, and account-help; or
2) “Chop billing” as a billing fraud/abuse practice (explaining what it is, how it’s detected, prevention, compliance, and how customer-service teams should handle suspected chop-billing)?
Tell me which one you want (or describe the exact meaning you intend). If you choose option 1, do you want current CHOP contact details included (address, phone, website) so I can provide specific numbers and URLs?