Can I make a $300 payment to reactivate phone
That would certainly depend on how much was owed. If your line has been suspended due to a past due balance, you would likely have to pay the full past due amount in order to have the line reactivated.
Regardless, you would likely get an answer by calling Verizon instead of posting on a public forum.
Calling Financial Services would likely be your best option. 866.266.1445