H2 Blockers like Axid and Zantac don’t seem to have the same success rate in treating infant reflux. My daughter was on Zantac and never got any relief. My son was on Prevacid and did much better. You can read about PPI meds for reflux at http://www.marci.kids.com
H2 Blockers are very weight senstive. She may have outgrown her dose already. My daugter had two increases in her dose in less than a month and eventually plateaued on it and the drug no longer worked for her. I’ve read here that that is common.
Is she sensitive to milk as well? She may have other sensitivities besides soy. Have you tried the Elimination diet to help find what other foods may be bothering her?
Her symptoms definitely sound like reflux, but she may have food senstitivites as well.
Good luck. I hope things improve soon. I sure know how hard it is.