How to send call by vb.net from pc to phone!!!
Or to make a button in vb.net application when clicked it send the call to phone which is connected by bluetooth

You may have to do this manually once before you figure out how to code this.

There is no real standard I see for PC Telephony. Your "call" could be on any number of apps and to send the call to the phone, that would be in the API of the app which you didn't reveal. This means no one can answer your question as you left out the details. Even with the details, the answer may be no if the app (Skype or others) may not reveal the API or support such a call transfer.

Thanks for your reply
Actually i made an application for the school teachers information where i work using VB.NET . So when you search about a wanted teacher a page containing his information will be shown .. one of those fields in the page is a phone number .. i want to put a button once this button clicked it will call that teacher by phone paired with this pc by bluetooth
Thats all

You've changed the spec. You lead with one goal, changed the goal and still have many missing details.

On top of that, I don't see an API to do what you asked so you might have to write an app for the (unknown) phone that your PC app tells the app on the phone to dial that number.

Sounds like a good project for a new programmer to find out about coding for phone and PC!

PS. Smart Phones SHALL NOT let any old Bluetooth connection control the phone natively. If it does either over Bluetooth or USB that is now called a security breach. Just last year this article at https://www.bleepingcomputer.com/news/security/smartphones-from-11-oems-vulnerable-to-attacks-via-hidden-at-commands/ brought this up.

Why this matters? Mostly because folk might plug in their phone to some free charger or allow a Bluetooth connection and well, game over.