Almost all companies will sell the Bitcoin as soon as it's paid, yes, most without ever touching it themselves. It's just like using a credit card as far as they're concerned. See this chart from BitPay on how they work: https://support.bitpay.com/hc/article_attachments/3600338995...

Remember that every actual Bitcoin transaction requires, on average, paying a $17 transaction fee to pay all the miners and the electricity they used in processing the transaction, so you don't want to actually be sending it between people often.

I have mainly used Namecheap and NewEgg, not AT&T. Many of these companies may not process Bitcoin transactions themselves, but instead rely on a third party like Coinbase/Bitpay who handle the BTC-to-fiat conversion, so in that case the companies would not themselves host a wallet. My "directly" I mean that you don't need to convert your BTC to fiat to pay for these services. I suspect that most of the companies would stop accepting Bitcoin if it couldn't be converted to dollars, but that's not what I was replying to; I specifically said that "prices are pegged to fiat".