Need to Chat With Online Customer

I have tour & travel agency and we handle number of clients in a day, via phone or face to face and in peak hours the process becomes more hectic. So, to ease the process we are looking for a live chat widget for our website. We have searched out many chat software, but still confuse in choosing best. Customer information security is our main motive. So, please suggest a software that is easy to access, safe and secure for our business.