If i add the 'data block', will I still be able to send and receive MMS??
No. Connection to Verizon's network IS required in order to use SMS/MMS. that's where your data charges are coming from. My phone doesn't have wi-fi but even if actual transmission is done over wi-fi, verizon's network is still required to initiate the sending and recieve acknowledments of the messages. If that is in fact all you are doing and using wi-fi for everything else, the data charges should be nominal. Shouldn't be more than about a dollar a month. Even if you have a message plan, I've read elsewhere that some get these nominal charges for data, and others not.

Here's an exerpt from another thread:

have unlimited sms and mms and pay-as-you-go-data, i have not been charged for any mms even though my phone will connect to ev-do. .... while it showed i had used data (obviously) it was not charged on my bill.

On another forum a poster said he WAS charged data fees but they averaged only about $,90 cents a month.

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My brain is so full of S (Entropy, that is), I don't know anything anymore.