Fallow are herding animals, rather than territorial. A major buck establishes a stand, where he makes himself attractive to does by a rhythmic belching grunt and by spraying the ground with urine and various hormonal additions. Each stand will have does wandering about and is likely to be surrounded by hopeful immature bucks.
Calling a roe by imitating the squeaks of a doe is inappropriate for fallow, where the females are attracted to the buck, rather than the other way about. Nor is a mature buck likely to stray far off his stand if he hears a distant grunt as if from another buck.
All one can hope for by imitating a buck’s grunts is to bring a big buck across his stand in defence of it and thereby offer a clear shot. That is, if you have managed to penetrate the ring of younger bucks which so often give the game away. As far as I know, there is no manufactured call on the market. Practice is needed, preferably in a deserted place and with the help of a recording.
There are some good DVDs on fallow available from the British Deer Society shop. For further details, visit www.bds.org.uk/shop.