could someone give me a good example of phone game? and how to apply sexual tension

*heavy breathing*

What I do that I learnt:
Day after you got her number:

1. Call and go "Hey its *name*"
2. Tell a quick, funny story (from your day usually) that u practised beforehand if needed.
3. say "Listen I gotta go *cool stuff*, hear from you later

some time after that: call her and invite her to something that you are doing with other people or whatever something cool. if she rejects you, she won't be thinking of you being alone becourse she rejected you, she'll be thinking you're still our doing awesome stuff.

p.s: I'm still new

Basically all you need to do is get some time alone with her to work on getting to the next level.

Your question's too broad. What are you doing that isn't working? Give some examples.

well. when i talk 2 her we always talk about boring topics or theres awakard silences. and i have this mellow tone voice and i just sound boring

Call with a goal in mind. Don't just call to hear her voice or get to know her. The long phone calls come much later. Have a plan, get coffe, lunch, ect. Keep the convo quick and to the point, have a plan that doesn't take too much commitment, and can be changed easily. Coffe as opposed to dinner and a movie.

Thats pretty much 100 percent the wrong approach. Well, there is no wrong or right with pua, but different schools of thought i suppose. But I disagree very strongly with your post.
What I usually do is write down some funny stuff that happended to me during the day and use it either as opener (= reason to call her) or if the conversations seems to die. For example, last week I called a girl after college and mocked those girls that come to the lecture all dressed up, in high heels and reeking of parfum. The conversation went for about 15 minutes and then I just said I had another thing to do and hung up. Don't be afraid to write down some notes. That's the beauty of phone game. You can literally have a script.
The whole sexual tension part is very hard over the phone because what phone game lacks is kino.

Another thing:
Phone game has two main goals:
1) Building comfort
2) Setting a date

But if you don't have enough of the first, you wont get the second. The more comfort you build the higher the probabilty she will agree to meet you in person.

Regarding lenght: I usually try to keep it between 10 to 20 minutes.

I hope I could help.