Cost of phone calls from a prison

ImproveHMPWandsworth

Has anyone any experience of the companies that offer a landline number for use in the prison which diverts to a mobile or device for a family? What should I look for. Some offer a service that means I can pay the whole cost of a landline call . Again has anyone any experience? 
An example is Phonesavvy , or c2c.

DullGreyGuy

ImproveHMPWandsworth said:

Has anyone any experience of the companies that offer a landline number for use in the prison which diverts to a mobile or device for a family? What should I look for. Some offer a service that means I can pay the whole cost of a landline call . Again has anyone any experience? 
An example is Phonesavvy , or c2c.

VOIP would be the obvious option depending on exactly what you mean?

It would just cost a call to a landline for the incarcerated person, people could put a VOIP app on their mobile etc and therefore there wouldnt be any additional cost. Alternatively it could be diverted to other numbers in which case the account holder would have to pay the call from the VOIP system to the mobile or landline or whatever.