I'm not sure what the distinction between 'web' and 'data' is. I haven't tried SSH or SIP -- mostly I am on home WiFi so I am not interested in trying out subtleties from my local fast-food restaurant, which is where I am when I want non-WiFi services.

Some people can only use certain web sites with their plans. I am not restricted in that way, anything is fine for me.

For your amusement, here is the red tape associated with our Prepaid plans. I haven't read it closely. Make of it what you will (There is a section guaranteeing unlimited data, FWIW):

Limited-time offer; all rates, offers, pricing and features subject to change without notice. Taxes and fees additional. Domestic only. Not all features or plans available on all devices. Unlimited features are only for direct communication between two people. Monthly Plans: Plan features available for 30 days; if sufficient account balance, plans automatically renew at the end of 30 days. If balance is insufficient to renew for 60 days, account will be converted to Pay As You Go. Pay As You Go: Service available for 90 days (one year for Gold Rewards) after activation/refill. After that, your account will be suspended and no service will be available. Gold Rewards requires activation of $100 in refills; you must refill while on Pay As You Go plan to obtain full Gold Rewards benefits. Pay-By-The-Day: Service available for 90 days (one year after activating $100 in refills) after activation/refill. $1 will be deducted from your balance each day you make or receive any call, including calls to voicemail and other calling features. If you sign up for plan more than one time in a day, $1 will be deducted each time. Day is 12:00 a.m. to 11:59 p.m., based on time zone associated with your phone number. If call spans multiple days (e.g., starts at 11:58 p.m. and ends at 12:05 a.m.), you may be charged $1 for each day. Nights are 7:00 p.m. to 6:59 a.m.; time zone determined by location of the equipment that connects the call. Weekends are midnight Friday to midnight Sunday. T-Mobile-to-T-Mobile calls are directly dialed between T-Mobile customer devices while on the T-Mobile USA network (and not roaming); calls to voicemail and other T-Mobile service numbers not included. Sidekick: Service available for 90 days after activation/refill. Service is $1/day even on days you do not use your phone. Prepaid General Terms: Sufficient balance required to use service. Calls rated on a per minute basis; partial minutes rounded up for billing. Void if not activated within 90 days from purchase. No cash redemption value. Non-refundable. Not responsible if lost or stolen. If you transfer your number to another carrier, your account will be deactivated and no service will be available. Devices sold for use on T-Mobile prepaid service are to be activated on that service, not transferred for resale, modification, or export. Messaging: You will be charged for all data sent by or to you through the network, regardless of whether received. Character length/file size of messages/attachments may be limited. T-Mobile is not liable for any failures, delays or errors in any T-Mobile-generated alerts or notifications. Data: Your data session, plan, or service may be slowed, suspended, terminated, or restricted if you use your service in a way that interferes with or impacts our network or ability to provide quality service to other users, if you roam for a significant portion of your usage, or if you use a disproportionate amount of bandwidth during a billing cycle. You may not use your plan or device for prohibited uses. Downloads: Additional charges apply; not all downloads available on all devices. Not all sites optimized for mobile browsers. You obtain no rights in downloads; duration of use may be limited; may be stored solely for use with your device. T-Mobile is not responsible for any download lost due to your error. Coverage: Service is not available everywhere; see Coverage Map at T-Mobile.com for details. Abnormal Usage: Service may be limited or terminated for misuse, abnormal usage, or significant roaming. By using service, you accept T-Mobile’s Terms and Conditions (including arbitration provision), located at www.t-mobile.com.