See if there is any sort of preference in YM for sending incoming messages to texts or phones, but besides that, there’s probably not a whole lot you can do.

Does this work?

Yahoo! Messenger for SMS?
http://mobile.yahoo.com/messenger/sms

Login to Yahoo Messenger via SMS:

Text to 92466 the following:
IN<space><YM Screen name><space><password>

after logging in, you will get confirmation from YM, and a list of your YM buddies with their designated SMS number. Your status will then be shown to your buddies as being on a mobile phone device accessible via SMS, which would limit their messages to 160 characters per message.

Call your carrier for help; you’re confused.

@thriftymaid it’s not a carrier issue. OP does not subscribe to data service. YM on SMS is the best option as per my ealier post.

@njnyjobs gotcha. I actually just read it as texts, which doesn’t require a data plan.

I stand corrected. @njnyjobs answer seems like a pretty good one.

@dverhey actually, there is an option on Yahoo Messenger app that lets your YM ID be automatically logged in on your registered mobile number. However, the SMS method of loggin-in is handy to have if your PC YM is not handily accessible or if you’re using an unregistered mobile number.