If it's a small nest then you can probably do it yourself but if it's a big one or you have an allergy to the stings then you might be better getting someone else to do it. If you don't want to do it yourself then your commune will tell you who to contact. Often it's the fire brigade but not always. Since last year my commune doesn't allow us to call the fire brigade anymore and we are now directed to a professional exterminator based in Vevey who does wasps, ants, hornets etc. The problem with that is how quick he comes depends on his workload and as Eire says, you'll be charged for the service