Why amazon didn't provide Tracking number when we Buy Shipping In Amazon?

we have issue to track our parcel in Amazon. We expected Amazon will provide the tracking number if we “BUY SHIPPING IN AMAZON” but it’s not there no tracking number provided and we have bunch of complain they dnt receive their parcel. it’s hard for us because we can’t do further because we dnt have the tracking number and we don’t have a business account with royal mail. can someone help us?