The potential scale of the alleged fraudulent billing operation is with little precedent in the history of Medicare, experts said.

The first angry calls to the Pretty in Pink Boutique began last August, confusing staff at the Franklin, Tenn., provider of wigs, mastectomy bras and other accessories for cancer patients. Medicare recipients from around the country claimed that a company called “Pretty in Pink” had charged their health insurance companies thousands of dollars for urinary catheters that they never ordered or received.

Flooded by dozens of complaints, the boutique launched a webpage in September to explain that its leaders were dumbfounded, too.

“We have reported the calls we are receiving to Medicare, and we have been working with callers to try to figure out exactly who is filing these claims,” Pretty in Pink’s website reads, asserting that another company by the same name was submitting the claims, and offering instructions on how to report the fraud to federal officials and insurance companies. “FRAUDULENT CLAIMS ARE BAD FOR ALL OF US, AND WE ARE ON YOUR SIDE.”

The complaints that ensnared the Tennessee cancer-care business are just one piece of an alleged fraud scheme whose scale has little precedent in the history of Medicare, experts said: an estimated $2 billion.