Patronising and unhelpful manager with no sense of urgency

I bought a Master combination lock on Sunday. I set the combination, locked it and opened it again with said combination. I then put it on a gate at my house. When I tried again on Sunday to open it, it would not open. It turns out the lock had changed the combination by one digit. I managed to open it and reset the combination to to the one I had set it to before. This morning, I have a plumber at my house but I cannot open the gate for them because the lock has reset itself to an unknown combination, not simply one digit away from what I had set. I phoned Builders customer care, had to tell them the story, only to be put through to the Newmarket store to tell them the same story, only to be put through to Roland the manager to tell him the same story. He did not believe that the lock would reset its own combination but said he would contact Masterlock and get back to me "in five minutes". "Five minutes" expired fifteen minutes ago! Roland does not seem to understand the sense of urgency of the plumber being here right now. As for him not believing this lock changes combinations on its own, I have been taking screen grabs now of this exact problem with Masterlock combination locks doing the exact same thing he does not believe happens. I find it insulting that he seems to think I do not understand how combination locks work. I have been using them for years. Perhaps he thinks the other buyers online are idiots based on his condescending tone. Please get someone to my house to either open the lock or cut it off. I want my R509 back for a lock that clearly does not work.