Panic attack

Can anyone help me how to overcome panic attack in public as i can't calm in type of those situations like when I am in alot of people or gathering places i became an silent most of the time, can't speak a single word, sweating and anxious, fear happened and that's waste my entire day.

I tell you another situation happened with me is that it is another day or I can say same problem day I went to the shop of the local market to buy some groceries and worst thing begin . first of all there are more customers in that shop and i became silent can't say to the uncle give these goods because of panic attack and fear of gathering and i remain silent until everyone gone . My entire day ruined because of this reason. So suggest me about this how to overcome in it.