I found the below verbiage regarding the migration of Alltel over to Verizon and M2M integration.   Here is what I found in the FAQ on Verizon's site.    If you get billed for your minutes to Dad I would use this as my proof that those charges should be reversed:

Yes, today Verizon Wireless customers can call Alltel customers without using their plan minutes.  Alltel customers will have access to mobile to mobile calling with Verizon Wireless customers on February 17, 2009.  Alltel customers will be able to use their mobile to mobile minutes for calls with Verizon Wireless customers without using their plan minutes.  Alltel customers will receive information with their bill in the coming weeks that informs them about when the expanded mobile to mobile calling community will be available to them.  Verizon Wireless now has the largest mobile to mobile calling community in the country -- 80 million customers.