Newbie T-Mobile tip: T-Mobile offers two separate interfaces to AOL Instant Messenger from certain cell phones: an SMS-based interface and a WAP-based interface. The SMS-based interface sends alerts to your phone when you receive messages over AIM, and lets you reply or send new messages by sending text messages to special phone numbers. As with all SMS messages, there is usually a per message charge for messages sent and received. T-Mobile also offers pre-pay bundles of AIM service for lower rates. To use AIM via SMS, sign up through T-Mobile's website. It is not necessary to sign up for a pre-pay plan to use AIM via SMS: the basic rate is 5 cents per message. The set-up process will populate your phonebook with the AIM codes.

The WAP interface is available through T-Mobile's WAP service, t-zones. t-zones costs $5/mo and includes a variety of other WAP-based services, as well as WAP access to the Internet. AIM is accessed through WAP pages, like other WAP services, and requires no additional set-up. AIM messages through WAP are no extra charge, they come included with t-zones's unlimited WAP usage. (As far as I know, there is no mechanism by which incoming AIM messages will send notification to your phone using the WAP interface exclusively.)

If you do sign up for AIM via SMS, don't use your regular AIM account, create a separate AIM account for mobile use. If you use your regular AIM account, like I did, conversations you have on your PC will be beamed to your phone, one message at a time, and bill you 5 cents a message. If you sign up for AIM via SMS and don't want it any more, "sign off" from the phone by sending a blank text message to the sign-off number T-Mobile provided (4647).

This distinction between SMS and WAP AIM isn't that clear from T-Mobile's web site. All they say is AIM access is free with t-zones, and they also provide a way to sign up for the (separate) AIM via SMS service, with only a hint or two that it'll cost you 5 cents/message. This is apparently an easy mistake to make: when I informed T-Mobile I had not intended to sign up for AIM via SMS, they granted me a small stipend to ease the blow of the accidental SMS bill. (Points to T-Mobile customer service for responding to my email within 24 hours.)