For many years I have used a service from voipcheap.com. The company that runs it has several different versions which you can chose from. Each has different call rates to different places with some being free. There is an app too for mobiles and Mac/Windows. I don't use it so much now because of Whatsapp, but it still helps occasionally. Call rates are usually less than Skype.

A comparison of all of the companies price plans is here:

https://voip-comparison.com/betamax#letter-U