Lack of in-network care for a doula

I have health insurance through my husband’s work; rather than being an insurance provider, it’s the third-party administrator, and the plan is self-funded. I’m running into some very challenging issues regarding out-of-network care. My plan covers doula care, but there are no in-network providers, so I would need to go out of network and do a reimbursement. The problem is they can’t tell me how much a reimbursement would be. They say there is no way to look into this because they are an administrator, not a provider. All they can say is it’s covered at 70% or Medicare allowable rates, but they can’t tell me what that allowable rate is. A doula can cost several thousand dollars, and I don’t want to invest without knowing what may be covered. Does anyone have a suggestion on getting around this? Also, is it legal to not offer an in-network option? I’ve asked about Gap Coverage but have been told that’s not an option, and I must go out of network. My husband’s HR is looking into it, and I’ve contacted the Department of Labor.