You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Sky_(United_Kingdom)

Context:
BSkyB initially charged additional subscription fees for using a Sky+ PVR with their service; waiving the charge for subscribers whose package included two or more premium channels. This changed as from 1 July 2007, and now customers that have Sky+ and subscribe to any BSkyB subscription package get Sky+ included at no extra charge. Customers that do not subscribe to BSkyB's channels can still pay a monthly fee to enable Sky+ functions. In January 2010 BSkyB discontinued the Sky+ Box, limited the standard Sky Box to Multiroom upgrade only and started to issue the Sky+HD Box as standard, thus giving all new subscribers the functions of Sky+. In February 2011 BSkyB discontinued the non-HD variant of its Multiroom box, offering a smaller version of the SkyHD box without Sky+ functionality. In September 2007, Sky launched a new TV advertising campaign targeting Sky+ at women. As of 31 March 2008, Sky had 3,393,000 Sky+ users.

Question:
WHat allows customers to get Sky+ functions if they do not subscribe to BSkyB's channels?

monthly fee