Language barriers

Moving back to Australia has (on the whole) been a good decision so far, despite various problems that just never seem to end.
But let me tell you about the problems I’m facing with my accent. My accent is getting very confused, and so are the people that have to interpret the words coming out of my mouth. It started off as a northern England accent many years ago and along the way has picked up bits of Australian , and most recently bits of Canadian (although no Brit, Australian or Canadian would be able to identify with my accent). In different places that I’ve lived I have had to adjust my pronunciation of certain words in order to make myself understood (and I’m not talking about tom-ay-toes and tom-ar-toes here, because I refuse to get into that).
There are several examples, but let’s discuss coffee for a moment, in particular mocha, which I am prone to ordering on a fairly regular basis. In Australia they pronounce ‘mocha’ with a short vowel sound, which would rhyme with ‘locker’. In North America it is pronounced with a long vowel sound, rhyming with ‘poker’. It didn’t take me long to adjust the pronunciation of that word when I arrived in Vancouver – it was a necessity because they didn’t understand what I was asking for otherwise. But back in Australia I am having immense struggles remembering to order it with the short vowel sound – it just sounds too weird to me now and I can’t believe I ever pronounced it that way before. The other day I asked for a mocha but accidentally pronounced it with a long vowel sound. The girl taking my order looked confused for a second but then set to work making it. However, a mocha she did not make. In fact I ended up being served a latte! How can she think that I asked for latte? It doesn't sound anything like mocha no matter how you say it. This morning I again asked for a mocha with a long vowel, and I got a very blank look from the barista. He just stared at me and after about 5 seconds said, "I don’t think we serve that". So, realising my mistake, I tried asking for a mocha with a short vowel, and he told me that they did make those.