Air Carrier Captain parked in the de-Ice pad reported Iceman advised them de-Icing was complete and they could taxi out. As they began to taxi Iceman ordered them to stop as they were actually still de-icing the aircraft.

Narrative

We were operating Aircraft X ZZZ to ZZZ1. Our aircraft along with several others were basically grounded waiting for the freezing rain/ ice pellets to change over to snow. There was a short window of time between the freezing rain and heavy snow that was approaching the airport; that aircraft could get de-iced and meet the holdover times. Our flight along with about 8 others; taxied out to the de-ice pad. Once a spot opened; we were assigned lane 1 for de-ice. Aircraft was configured; and de-icing was initiated. Iceman came over the frequency and said: 'Aircraft X de-icing complete; type of fluid used and the time. You are clear to depart the area; contact ground for taxi.'We re-configured cleared left and right and received taxi instructions from ground. Brought the power up to taxi and moved about 20 feet when Iceman frantically yelling over the frequency for [our aircraft but with incorrect flight number] to stop. 'Aircraft X STOP; STOP; Aircraft X STOP'. Now remember we [had a very similar flight number]. I immediately slammed on the brakes knowing we were the only aircraft that was probably heading out of the pad. I looked back to the left side as far as I could see and there was the boom truck between the wing and horizontal tail area with the boom and bucket still extended. The look of the Boom Operator said it all. I asked Iceman what is going on; he replied that he gave the wrong flight number and they are still spraying our aircraft. I verified with him our tail number just to make sure we were on the same page. Again he apologized profusely about the mix up.Obviously this was a serious situation that could of ended up with someone being seriously injured or worse. My opinion from all of this was a combination of oversaturation of aircraft to get the planes out before conditions got worse; non standard use of tail number vs flight number; and confusion as to what flight belonged to which aircraft. De-ICE crew over saturated in work; pressed to get many aircraft de-iced before the heavy snow came; confusion in regards to flight numbers and tail numbers. Review De -ice procedures; discuss how this could be averted in the future; discuss if there needs to be operating changes in how we de-ice at particular stations.