Cell phone calls should be a personal affair.
It doesn’t matter if it is a business associate or your closest friend on the other line, do not subject others to your dirty laundry. Keep your voice down and try to find a low-key location if you must speak in public places, like a street or restaurant. It amazes me how loud people can be when talking on the phone out in public, which just screams, “Hey, I’m super needy and want everyone to know I exist.”
Be courteous to both friends and strangers alike by not forcing them to hear the details of your break-up or business negotiations. Move to a different spot, or don’t talk at that time. Really, we’re just not that into you.
Also, please say, “Excuse me,” if you must take a call in front of others. People just answer there phones now even though they may have been mid-sentence with a friend or family member at a restaurant. Show courtesy to the person you are with by pardoning yourself first. But better yet, show the person you are with that they are truly important by silencing your phone and letting the call go to voicemail.