How to hook up Apple Watch 4 to ATT prepaid cellular account?

So I have a series 4 watch and want to add a plan to my already existing ATT prepaid account. I refuse to transfer to a contract ATT account since the same amount of data I get with prepaid account at $40/month would cost me $70/month after tax. Why would anyone pay twice as much for the same speed and amount of data?!! So Apple how do I get my Apple Watch 4 hook up to my att prepaid account?? I paid extra for the cellular version and I can’t even use it? Please fix this. Not cool. I should be able to add the $10/month watch cellular to my pre-paid account. But it looks like I need to pay twice as much for same service plus the watch $10 which would then cost me $80/month to use my watch. So really it will cost me $40/month just because I want to use my watch??? Apple better fix this fast. Or I want my money back for what I paid extra for the cellular version on my watch. ;( not happy about this. And I can’t be the only one.