Verizon used to offer this with OneBill thru its Fios system. I don't think that this is allowed any longer because it caused more problems than it was worth since Verizon Wireless and Verizon Fios actually operate as 2 separate companies with the same parent company.
People who were on OneBill were not able to enter into any phone purchases with the monthly payment option. Changes to your Verizon Wireless account were also prevented unless you cancelled your enrollment in the OneBill program.
So it was disfunctional then, and instead of making corrections they just scrap it? This is not at all convenient for their customers who have both Wireless and Fios, yet Verizon is completely happy ignoring the needs of their customers. Wow, really seems like they cherish our business, huh?