When the sponsor enrolls family members in MetLife, pay attention to the effective start date. I know this seems obvious to most, but my H clearly didn't pay attention when he enrolled my daughter online. Now we have a $120 bill for a 5 min appointment that consisted of briefly brushing her teeth and looking in her mouth. H enrolled her on Sep 22, so she is not covered until Nov 1st. Had he enrolled her 2 days earlier she would have been covered.
Yes, you have to be enrolled by the 20th of the month to start on the first of the following month. This is to stop the people who get a tooth knocked loose from running online and signing up so they can be seen the next day (kinda like buying car insurance after getting in a car accident.) That being said, call the dentist. Something similar happened to us. Both DH and I are active duty and when our first child was old enough for the dentist I called the base dental office. They told me they didn't see dependents, but we could go to any dentist that took Tricare. We'd never had/been dependents before and had NO idea we had to pay for additional dental coverage; the base dental office never mentioned it, they just said go to someplace that takes Tricare. Anyway, we got a $100 bill for the same thing you mentioned. I called the dental office and explained/complained that the "cleaning' we were billed $70 for was brushing her teeth, and that no one had confirmed our insurance prior to being seen, as most places do. They reduced the charge to just the dentist's exam, and didn't charge us for the cleaning.
Ah, thank you. I called the dental office and the lady I spoke to was super nice. She said they only charge $25 for little ones who are not covered, but $120 to insurance companies for those with coverage. Kind of jacked up, but lucky for me.