A bigger, better antenna might help, or just be a waste of money. Google "Hypergain" for carrier-grade antennas.
The OP will have to do a search for his exact frequency in his exact location (with his carrier and his level of service). But with the right antenna ten times a teensy bit can become a little bit, which is sometimes enough, in my experience.
If it is just voice, I would walk around asking others if they have any reception, and then buy a prepaid burner phone with whichever service is working.
A metal trailer cannot be an antenna but if the treailer has a metal roof it will help as a "ground plane", which removes stray signals bouncing off the ground before they hit your antenna.
If the OP knew exactly what freq and where to point it, he could buy a 4-foot parabolic dish from Hypergain and it "might" work. But long before that I would do the recommended online search and educate myself, because it is very, very complex stuff.