Reduce Mobile Phone SMS and Call Costs

What would you say if there is an easy way to reduce mobile phone SMS and call costs ? I’m using a service called Cellity for some time now and was able to reduce my mobile phone bill tremendously. I do write the occasional SMS which usually costs between €0.10 to €0.20 per SMS. Cellity reduces this to the cost of the data transfer rate of the SMS which is just a few Kilobytes the most.