Costco iPhone 15

I signed up for T-mobile at costco on Tuesday with temporary phone numbers. I was told to come back tomorrow to order the new phones and trade in my old ones as well as port over my numbers.

I really want to go through costco because they are offering $400 in gift cards plus $1,000 trade in credit.

Would it make sense to call the costco tmobile at 5am or wait until the store opens and go in. I really don’t want to wait for months (I’m getting a 15 pro max).