I have a basic phone plan with the 300 message minutes and unlimited data plan for $15 per month.
Verizon has been clawing away two counts for every picture message I handle. I don't run "apps" on the phone. I only use the basic phone and the integrated messaging service on Verizon official page which does not say it will count as double usage.
For each MMS pix message sent or received, it deducts two credits from my account and appear as a pair of usage on my account.
For example, a picture message I received caused it to get billed as:
04/17/2016 at 03:56:55 PM Pix Message - Incoming
04/17/2016 at 03:56:12 PM Pix Message - Outgoing
I've reached out to chat and was told it wouldn't happen again two months ago, but it is happening again.