1) The event company is still not big enough for the use of walkies-talkie.
2) The even company is still not big enough to require the use of walkies- talkie.
3) My work partner call me/page me on walkies- talkie when he needed something from the store room.
4) He's paging for you/calling you on the walkies- talkie.
In all cases you need walkie talkie (you'll sometimes see it hyphenated) or walkie talkies in the plural.
You call someone on a walkie talkie. A pager is a different gadget.
Please note that Walkie talkie would have been a better thread title. I have asked you before to give your threads more meaningful titles.