You can go to the Sky Sports channels in the EPG and press the red button to add the Sky Sports from there.
It might be worthwhile speaking to regrades as well, and see if you can negotiate a deal by switching to the Bigger Bundle plus Sports. ( bigger-bundle-sports )
You can call 150 from a Virgin landline, or 0345 454 1111, options 1,1 and 4 (Changes to your package) butbest to call at 8am to avoid call queues or mid afternoon around teatime.
You could try the text messaging service. Just send a text with a description of regrade to 07533 051809. Your message will go into a queue and a representative will respond to you as soon as possible. It may take a few days.
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali