Skype

How to use SKYPE the most economically on my cell phone? I have a T-Mobile (US) prepaid account and I have a smart phone E-TEN M600 w/ preinstalled Skype.I’d like to be always Skype conected,but the monthly data plans are more expensive then a voice plans.I want to use Skype 100% of the time.What are my options to do it?