HTC's upgrade of the HTC Sensation on Wednesday to Android 4.0 will be bittersweet, as a T-Mobile representative said that the company will begin enforcing its $14.99 per month wireless hotspot plan.

HTC's upgrade of the on Wednesday to Android 4.0 will be bittersweet, as a T-Mobile representative said that the company will begin enforcing its $14.99 per month wireless hotspot plan.

That probably means that the carrier's policy of letting some customers use the feature for free will end, making a Wi-Fi hotspot subscription mandatory for those who want the "Ice Cream Sandwich"/Android 4.0 upgrade, and wish to keep using the phone as a wireless hotspot.

T-Mobile's support document on the HTC Sensation upgrade on Monday came with a caveat: "HTC Sensation 4G will be required to add Wi-Fi Mobile Hotspot feature in order to use the service after completing this update."

T-Mobile also indicated that ICS would be coming to the "in the coming weeks". However, that document lacks the Wi-Fi Mobile Hotspot caveat that T-Mobile included on the HTC Sensation page. On the other hand, users have reported that T-Mobile has also previously blocked the Wi-Fi tethering feature on the Amaze.

T-Mobile has always officially charged $14.95 per month for Wi-Fi hotspot access. However, some users were given a free pass, leading to confusion about whether T-Mobile actually charged for the feature. Users needed to buy the package, whether or not they used a USB cable to tether the phone to their computer, or a Wi-Fi connection.

"T-Mobile began offering a Smartphone Mobile Hotspot plan in November 2010. However, due to technical limitations with software, customers were not being charged for the feature on select T-Mobile products," a T-Mobile representative said. "Customers who choose to upgrade their HTC Sensation 4G to the optional Android 4.0 (ICS) software update will be required to sign up for the $14.99 Smartphone Mobile Hotspot plan."

Furthermore, some users were also given a grace period of sorts. "T-Mobile may not immediately block you from Wi-Fi sharing until it is verified that you are using your device as a modem...and at that time you may be blocked and then required to purchase a feature to continue using it," a T-Mobile customer support representative wrote last year. "That said, there may be a period of time where you are able to tether without having the feature added on the account."

Although a T-Mobile representative confirmed that HTC Sensation 4G customers who wish to continue using the hotspot feature would need to pay the extra fee, all HTC Sensation owners will be able to upgrade to Ice Cream Sandwich for free - it's just the hotspot feature that will cost extra.

, as it said in March, including the Droid Incredible 2 by HTC, HTC Amaze 4G, HTC Desire S, HTC Desire HD, HTC EVO 3D, HTC EVO Design 4G, HTC Incredible S, HTC Sensation, HTC Sensation XL, HTC Sensation 4G, HTC Sensation XE, HTC Raider, HTC Rezound, HTC Rhyme, HTC Thunderbolt, and HTC Vivid.