It would be interesting to know how this fraud got pulled off exactly and what security measures were in place to detect and avoid it in the future. For example, did somebody call Verizon and claim to be you (somehow provide information from your Verizon bill) and once verified, proceed to request SIM cards to be sent and activated with additional phone numbers, or even worse, phones? Which address would they have sent it to, and if not your home, how could they have obtained the items (porch pirate, Verizon store in-person identity fraud)?
If they did this online, and logged into your account, could they have added services and again, to what address could they have sent the items? Or did they arrange to pick up at a store and then get the items by showing false credentials? Who verified they were who they claimed they were?
Finally, this possibly was NOT a malicious criminal act but just a case of an internal mix-up by an incompetent Verizon employee who keyed in the wrong number and cross-linked unrelated accounts. It is good that they are reimbursing you for the screw-up but hopefully they can explain how this happened so you and others can learn how to protect ourselves from this in the future, especially if this was a "hack".