I work for T-Mobile's tech support but will remain anonymous.

All customers should have the wap.voicestream.com APN on their account regardless of features added to their plan. It's what gives users the ability to download ringtones, etc. to their handsets regardless of make/model and is also used to pipe data for browsing on your BB (primarily used to give GPRS access to most devices). There's no charge for it and you shouldn't need to subscribe and in fact there's no way to remove it. I am assuming, however, that you have opted for the BB option on your account for $20/month for the BIS? This gives you Wap and blackberry APN's on your account.

Finally, many reps may not necessarily recognize the ability to access other TCP functions on your device beyond browsing on port 80 as nothing was officially recognized as "changed" or "unlocked" to my knowledge.