I don't think one should ever depend on verbal commands. Verbal commands only really work well when the other points of control; seat, leg, hands are working well, too.
A horse that comes behind the bit is much harder to deal with than one that goes above the bit, but, one thing to do is to NEVER apply both reins equally. Instead , you utilize the One Rein Stop; you give him one rein to follow, and some leg to make him move forward, and follow that rein around in circles, small circles, until he decides to give to the rein and stop.
You need a good riding buddy who will help you while you work on this, and will not ride off and make your hrose flip out when you are circling him, but will patiently wait for you to get that one rein stop. Then, the two of you will walk on. Don't do any trotting or cantering until he will stop pretty quickly .