If your attempts at resolving the conflict and trying to come to an amicable outcome have failed, then it may be time to take it to those higher up. Your manager or team leader might be your next port of call, try explaining to them what has happened, both sides of the conflict and why it is still continuing. If that still doesn’t work or if they are part of the problem then you might have to take the conflict to someone else senior in the business. You might also try your HR department (even if it is external).

If the problem continues, you might want to start taking a diary of notes to build a case history, this might become a problem of workplace bullying/harassment.