What would be a good introduction to a telephone survey?

I am conducting a study by telephone about grocery stores, and would like to know how could I improve my introduction to get more people on the phone and therefore more complete surveys.
Here麓s the introduction that I am currently using:

"Hello, my name is _______ I am calling from (name of the company). THIS IS NOT A SALES CALL, we麓re just conducting a study about grocerie stores in your area and would like to include your opinions"

I don麓t know why is so hard to make people understand that if they express their opinions, they麓re going to help to improve the products and services that they purchase, but most part of the respondents hang up the telephone on the introduction.

Any tips to improve my introduction and therefore get more people on the phone?? I mean, If you were the the respondents, what kind of introduction would make you answer the survey?

Try, Hello, my name is calling on behalf of _, we conduct opinion polls on grocery stores in your area.
I would then go on to my first question. Being assumptive is a key part to making phone surveys or sales. Just assume that the customer is going to participate and move forward with that.
It may not be what you are saying as much as how you are saying it. Be sure that you are using good voice cosmetics.
Stress the words you want to get across or that you want to stand out. Watch your pitch, watch the upswing in your voice. Avoid sounding robotic or monotone.
Pace is important as you don't want to talk so fast that you are not understood and you don't want to talk so slow that they lead gets tired of listening to you and hangs. Your tone of voice should be pleasing, polite and courteous.
Good luck!