You can forward calls from your existing phone to another phone by changing the settings in your existing phone. You can use either a Network Operator Short Code to forward calls or you can use instructions specific to your handset brand.
There is no cost to set up forwarding of calls, however there may be a cost per minute that you incur. The cost to forward a call to another number will vary depending on your service provider. Please contact your service provider to find out the cost. You will need to tell them the number that you are forwarding calls to.