£50 charge for 'Tune Up'

I have just noticed an extra £50 charge on my monthly bill for Virgin Media 'Tune Up'. I have never heard of this service nor have I requested anything extra that would warrant this bill. Google search reveals nothing other than one other user who has complained about this false charge. Virgin's team told me it was a music service that I have signed up to which is an outrageous lie. I'm a 21-year-old tech-savvy student, so I'd know if I signed up for a music service, especially when I already use spotify. I complained and they're sending an engineer out, and if somehow the engineer believes I did sign up to it, not only will I have to pay the £50 charge but also a £25 engineer fee. Knowing Virgin, they'll probably lie and say I did sign up to it. I refuse to pay my next bill unless this charge is removed. After my contract ends, I will run as far away from Virgin as possible, it is a rotten company from top to bottom.