Stammering. With customers properly!

I am 30 years old, I am working in cyber cafe operator since last 9 years, i have stammering problems since school times, Generally when i was 4th standard i didnt stammer, i was very much fluent in speaking, I remember my speach in school time when i was in 5th standard, after that I dont know what happen to me I started stammering and i am not able to speak in publicly or unknown person or in interview, group discussion, but in family mostly i didnt stammer mostly words, but outside i stammer in mostly words, when i see more people i became little bit depressed and my tongue and lips do not co-ordinate same way. some times words not come outside. it creates very much shame full situation in certain times, i have very much ability but due to this problem I mostly became silent in any topic because i know if i speak and i shutter peoples laugh on me. Now it is effecting my business. I can not explain my plans, schemes or other details with customers properly