"among" is used when you have a group where individual members are not specified: "Among the ten colleges, at least one was Ivy League." "He was the most handsome guy among the men that night." Here is your original with several corrections: "Among the many benefits available to customers are discounts on our other services, such as satellite TV, home phone and fax lines." I would actually recommend going with "include" instead of "among": "The many benefits available to customers include discounts on our other services, such as satellite TV, home phone and fax lines." Note that "between" is similar to "among", but used if there are distinct items specified in the group: "He needed to choose between Harvard, Stanford, and MIT." "For her date that night, her choice was between Bob, Mike, and Joe." Note that there is a common misconception that "between" is used when there are two items and "among" when there are more than two. The number of items doesn't matter -- only distinctness matters.

"among" means in with a group. There were many tall men among them. There was one slice of cake among the many desserts. Mongolia is among one of the least densely populated countries.

Thank you everyone

Don't forget we can say 'amongst' too. Maybe not as common but you'll see it. I use it habitually. "Where's my favourite sweater?" "Somewhere amongst that pile of dirty washing!" "Oh dear!"