Save location for mms
 

I have a i910 (verizon) and I use Youmail to get my voicemail. I am getting my voicemails as mms. alot of them are work related so I would like to keep them for a long time in some circumstances. It appears that it is saving them on my device not storage even though I have email attachments saving to storage. I have read people talking about there being a tweak to change the save location for sms, but I have not been able to find it. Anyone have any ideas?