Different type of approval?

So i got a called last friday to say that i was approved...the lady was was talking on the phone but all i could hear after that was waaaah waa waah waaaa wah ( i was just zoning out from finding out) and i asked if the approval was for insurance says yes, that there is more paperwork to do and that a few more appointments before actual surgery (she hasnt given me any dates for anything so far) i was like ok ....but then i wanted to double check just like a lot of people do so as to cover all my bases. I call bcbs of mi and asked if surgeons office sent info to get approval.. says that no they havent sent anything but that is not so much as a paper approval letter from BCBS but that all 6 month diet and phsyc documentation the surgeon had to have in my file and once his office would get that info. that the surgeon needs it to document just incase he gets audited. I have really good insurance where they pay anything and if there is copay or anything left we have a card that is given by his employer to pay for it. lie a benefits card. so I was wondering.... have any of you dealt with something like this? I thought i was to get a proper letter of approval from insurance.