Ditto to Linda H's comment. These guys have a serious problem with their billings. In August 2016 I got a letter from a collection agency stating I owed VA almost $2500. Do they really think I am going to fork over $2500 without questions and how was I going to trace that back; how did I know I hadn't already paid it? It's not my personal policy to not pay my bills for two years. I sent them an email wondering why I should believe I owe them $$$$ when two years had gone by, not to mention damage to my credit and interest accrued. So two days later I get a call that oops, your bill is actually $0. I have wasted a load of time trying to get this straightened out. I called back requesting they send me something in writing to share with their collection agency and suggested they clean up their act. The woman I talked to was indignant and rude and I didn't even get an apology until my ranting reached a fever pitch.
My advice: If these guys are working for you make sure you hold onto every piece of paper they send you. Make a copy of your check. Set it aside in a separate envelope and file it under the taxes for the year of your procedure in case they decide they want to pad their billings in two years.