Depends on your current plan allotment. 1GB plans run $15 for 500MB and 2GB and up run $10 for an extra GB. I believe it costs less to do so by doing this yourself rather calling it in to change. Also, backdate the change if on contract to the beginning of the cycle. However, remember that if you have 2 GB and you up add 2GB but it is halfway thru the cycle that you will only get 1GB, meaning a total of 3GB in the cycle. Just do so before the end of the cycle. (above was just an example) We can be more exact if we know your actual plan.