Where do you work that you know all about the horrors of used mattresses? I’m just curious.
A quick google came up with this: [Resolved] PODS Enterprises Review: total scam with tons of hidden charges! - ComplaintsBoard.com
I would suggest calling the place you bought it and asking them.
I once sold a wrought iron bed frame, mattress, and box spring set on eBay asking for local buyers only to avoid the shipping problem, but some lady in Texas really wanted the thing and won my auction (I’m in California). So I called all the shipping companies I could find operating in my area and one of them took it for $200 despite the weight and size issues. Unfortunately, I don’t remember their name, though it was a smaller company. But the set did get to her very quickly and in perfect shape…
Once and for all, I am NOT GOING TO SELL IT AND BUY A NEW SET. Ahem. Sorry about the capslock thing. But it cost $700.00 new. I am not sleeping on a cheapo set ever again if I can help it. I am not getting rid of it (very unlikely that I could get much of anything for a two-year-old set, which this is) and then turning around and spending $700.00 ten days later on a new replacement set.
I now have a new plan. 
It’ll cost about $15 a box, up to 70 lbs. per box (including tax and the new UPS box itself, also shipping tape) to ship things by media mail through the USPS. Books, DVD’s, photographs, sketchbooks, records, and anything that could possibly be considered any kind of printed/written material can be shipped this way. If enough space could be cleared out for the mattress and box spring, then voila! I really think that this could work…
Oh, oh yeah, and the question about where I work and the horrors of used mattresses! Okay, first of all, this is advice that is absolutely all over the web anyway. Even the most wild-eyed cost-cutting sites say NOT to buy used underwear, makeup… and mattresses. But my personal experiences… no details will be gone into. Let’s just say that I work at a nursing home and hospice.