The person that refilled the system should have sorted this out - did the system ever work properly since this was done?
I take it you have an open-vented CH system - the type with a small overflow / refill tank in the loft?
Normally the CH pump is perfectly capable of pushing any residual air out of the system. It pushes it along to the next rad, where it rises to the top of the rad and sits there as it can't get down to the bottom again. That's when bleeding is used to get it out.
If however, the airlock is in the vicinity of the pump itself, the pump spins in fresh air and no water gets pumped around. In that case, running the CH causes what little water there is in the boiler to overheat and boil, making the dreadful noise and locking out the boiler.
Systems should be designed so this doesn't happen - but installers sometimes put pumps in the circuit in unwise places - where air can sit around the pump if the whole system is drained. Look at the pipework in the area around the pump and around the boiler - sometimes there are drain valves located. Try opening these one by one and attempt to extract air.
PS - it is just possible that your pump is knackered - just because it hums doesn't mean it is doing anything - however given the recent service work, it is most likely to be air around the pump.