Welcome to the forums. My suggestion would be to change your plan to one with more minutes. For example, you state you are on the 450 minute plan. That plan is $39.99. You can, for about $30 bucks more, have unlimited talking. Or, you can switch to the 900 minute plan for about $20 dollars more. One thing about Verizon is you can change your plan anytime you want without any problems. You can use the My Verizon feature found in the menu above and change your plan or any other aspects of your account at any time. After your trip, you can switch it back. Now, I am not sure if you are on an older 450 minute plan that is cheaper than the current 450 plan that is advertised. You may not be allowed to switch back to such an older plan. You would have to switch back to the 450 minute plan that is currently offered by Verizon. Either way, going temporarily to a higher minute plan while on your trip will help you. I hope this information helps.
Dont do it online.. I had the 450 plan switched to 900 minutes and still got charged for overages. I called the customer service and she told me because I didnt back date it.. They couldnt help me, now I know they could. They can do anything. They wanted to give me addtional minutes. But not any money back.... all because I did it online.. She said If I had talked on the phone with a agent I could have gotten it done right.. Very upset with Verizon.