We all have off days, maybe the tears were of frustration at not getting yourself understood or not understanding the phone situation.
Please do not let this put you off from going into town, I would suggest you go asap to prove to yourself that it was a one off and you are ok.
If you start to feel overwhelmed again stop what you are doing take yourself away from the situation have some deep breaths and get everything back into perspective, think about things you do well and achievements you have made.
Distraction activities also can help, think about the last 7 days meals you have eaten, recite a poem, name every relative you have or anything else that occupies your mind until you are calm.