Q: Want to buy apps thru my phone bill. But where payments is at it doesn't say phone? How do I get it to convert to my phone bill

It's news to me but appears doable, see link below. I'm going to asks the hosts to relocate your post to the Using iPhone Forum. Someone there should know for sure.

Set up mobile phone billing as your payment method in the iTunes Store, App Store, or iBooks Store - Apple Support

Depends on your carrier and whether they support it. In the USA if you allow them, AT&T will let you purchase almost anything online, including third party subscriptions and have it billed to your AT&T statement through the AT&T mobile purchase marketplace.  If you use the feature you are also then open to all sorts of unsolicited texts, ads and other spam from AT&T marketplace vendors, not to mention your phone account now has a complete history of your online purchases which AT&T can sell to marketing companies.  There have also historically been problems with account hacks and unauthorized charges.

Personally, I wouldnt do it and I have AT&T purchase blocker provisioned on my account.