more than likely if no air came out, then the rads probably need to be balanced. You can do this yourself but if you can get the person who did the work to come back it'd save you a bit of messing around. I did it before and it involves tweaking the outlet valve (the other end of the rad to the temp control vlave) on one of the rads thats working and seeing if it has an effect of allowing the cold rad(s) to heat. e.g. by closing the outlet valve slightly on a working rad it may allow the heat to go to the cold one. Takes a little bit of time and patience though. I think the theory of it is that the working rads are taking too much of the heat and this is balanced out as described above.