It's not even a language issue, more of communication :) As one of my good teachers repeats once in a while, the key question is WIIFM - What's In It For Me?

In other words, you have to phrase your invitation so that it explains why it's good for them to do it.

As for the English, the thing that unmistakably works for me in writing is "I would appreciate if you could..."  

Good luck with persuading :)

Oi Nened,

Kaamos has already given you the right information.

Now I just thought of giving you a few Examples of Polite Requests.

1)I would appreciate it if you could provide me with your phone number.

2)Could I have a glass of water, please.

3)Could you tell me how much it costs?

4)Would you mind opening that suitcase?