Only problem with changing your number is you may end up with one that someone else has 'got fed up with' in same manner as you. I once had same phone number as the weather station that fishermen rang up for their forecasts.... (different exchange so if they forgot to dial the first bit I got the call - not fun at 4am in the morning)
If you are in the directory they'll get your number for free. Best bet is to go ex-directory and register with TPS and eventually the calls will diminish.
Some on here have call-blockers on their phones so may be they'll post with recommendations of what they use.