Text messaging using data only

[canadiankorean]

Hi,

I searched and searched but I finally give up.
Is there any application that sends text messages using data and not the text messaging service?
Something that is seamless and isn't done through a web browser.

I see a few threads regarding SMS through VOIP but that is something I am not looking for.

Here is the reason for this search.
I have a data plan that is unlimited but I don't have text messaging included with my plan.

any direction would be appreciated.

thx