You are, unfortunately, very confused about how the device is going to work.
Those "prepaid calling cards" that you are looking at are for someone to use who already has a phone number (typically a landline) and wants to make international calls at a lower per minute price.
If a person wanted to use those cards with a cell phone, that person would still need to have an active cell phone plan (either prepaid or contract) with a cell phone service provider in addition to using the calling card.
And using the calling card would use the minutes on the cell phone in addition to using the calling card minutes.
But your initial problem before you even get to that is that the cell phone you have is not active on an account that you control. That's the very, very first step that you will have to take care of. And if the device is still registered to another account, you are completely out of luck unless you can get that account owner to release the device from their account.
Be aware that Verizon requires a data plan for any BlackBerry activated on their network. If you want to use the device on prepaid, then you need to look at their prepaid options. The lowest plan is $65 per month.
Prepaid Phones & Prepaid Plans | Verizon Wireless
As to the MEID issue, does the Options > Status screen show an ESN number? If so, that's what you need to use.
Your larger problem seems to be very obscure. You have been trying to call people using Google Voice, but those people are not answering you because (for whatever reason) those calls are going directly to voicemail. I've never heard of that issue. But (assuming these people who you are calling actually want to talk to your) perhaps a more simple solution is for you to get one of the prepaid cards you were looking at and using it from a payphone (although they are difficult to find anymore) or from a friend or family member's landline phone. And skip the whole cell phone avenue.
If that's not what you are trying to do, can you give more details.