Settling medical bills

I went to a GP on their network list and he referred me to Suikerbos Medical clinic for x-ray scan, I went there did the scan everything was fine but when I went for a 2nd scan the clinic advised me to pay upfront and my medical insurance will reimburse me. I did so and the clinic told me that my 1st account was not settled by my medical insurance, and I have been receiving bills from the doctors requesting me to pay, I forwarded the bills to my medical insurance for them to settle the accounts. to my surprise I got an e-mail from my medical insurance stating that I should pay and they will reimburse me. My problem / question is why should I pay and complete the reimbur*****t form then send it to them and wait to be reimbursed, where else they can easily settle the bills as I have sent them the invoices.