How can you save more outbox text messages on your phone?

I have the Alias verizon phone, and i have an extra memory card but for some reason my phone will only save 30 outbox texts but up to 50 inbox texts. other verizon phones can save 50 of each|||I think that's just how it is, you can't save more then 30 msgs in the Outbox OR maybe that's becaus you have to many MMS messegs there and your phone can only save 50 SMS messegs, Contact Verizon for more info on this.