Unprofessional/ Disgrace

this complaint has been lodged several times with the supplier and still not solved. they send out different technicians, and all just say its not there job. this is the latest reference they gave me 99BWK031115 and an escalation number 775312. this has been going on for months now. the last person that was here, said his going to speak to the boss. No feedback as yet. What do you do in such a case? I lodged 2 complaints at the time, this is the old references 347CWK140915 and SM149063.