My phone connects fine using Your Phone companion app to my PC it just wont make calls, and I was wondering if I installed a dongle, would that make it possible to make calls using an external Bluetooth dongle to use that feature.
If you purchase and connect a Bluetooth USB dongle, then your PC should behave just like the Bluetooth radio was built in. So, yes, what you describe should work just like a computer with Bluetooth built in would work.
Other Answer
Yes, it would. Just make sure the dongle supports Windows 10 before purchasing it. If you really want to make sure that you buy the correct dongle, you can do some research on the website of the Bluetooth dongle seller. Buyer reviews are also great help when purchasing something like this.
By the way, I would recommend Bluetooth 5.0 if your computer has a driver that supports it. However, that doesn’t really benefit you if your phone doesn’t have Bluetooth 5.0. If your phone doesn’t have Bluetooth 5.0, Bluetooth 4.0 is great too.