There are many different companies supplying services such as you describe.
Some will allow you to phone in on a local number which may be free to you, from your standard telephone, and from there phone the long distance number you need to connect to. The call is made over VOIP between ends and you get charged for the termination and a little profit.
Some locations are free -- no charge at all.
There are differences between the charges of differing companies so you might save a little more by using the company that gives the best rates on the type of call you wish to make ..... destination and landline or mobile.
Two such providers that I accessed today are linked, and they have differing charges for their calls, although their service is essentially the same ....www.voipwise.comwww.smartvoip.com
There are lots of others out there.
The only hassle is finding the one with the smallest charges for the calls you wish to make.