My original answer about improving confidence was a bit vague haha, I think it depends. The only way to improve confidence is by giving yourself more challenging interactions, i.e instead of ordering at a quiet cafe, try ordering in a busy queue at a fast food restaurant for example. I think it's about trying different situations such as drive thrus or ordering on the phone too. Hopefully afterwards, you should feel better about yourself either for a) having a successful/improved interaction or b) for pushing yourself despite it not being the best interaction. Feeling better multiple and multiple times should reinforce confidence and hopefully improve fluency.