Just let them wait! Even if you have terrible blocks, so what? You're won't piss them off by stuttering. In fact, if you just keep going they most likely won't even care. Don't try to think of other words, just focus on that word - and no matter how long it takes to get it out of you, keep on going and say, in this case, 'thank'. If they did not understand because the blocks were so bad, just repeat yourself. If it was still bad, repeat yourself. Keep on doing this in all kinds of social situations and you will simply stop caring about your stutter. You have your stutter, there is no trick to fix it, in my eyes. Only by actively trying to improve your confidence in social situations and speaking will you overcome your fears and doubts.