Firstly - why do you want it changing? What problems do you have? If its faulty then VM will simply swap it for you when you call it in as fault. Calling at 08.00 is the best time to get through quickly.
Re. the link - Getting the "Ooops - please call" message, usually means you are on an old package that the computer can’t recognise so they want to speak to you about it and get you to change to a newer package in lieu of a new 18 month contract.
When you call it in, the agents will probably (unless you get lucky) know absolutely nothing about the scheme and say "oh no, that's an upgrade there will be an ctivation charge and it starts a new contract". Neither of those statements in correct. So they will discuss new packages and these can often be worth hearing about as they might offer you more things for the same (or a little bit extra £) - but of course you can just always say "No thanks" and leave the call.
After that you could try texting on 07533 051809 - include account name/number and what the issue is and see what they say – replies may take a bit longer
Finally, a VM person should pick this up here and sort the swap for you, but it can take a week or more for them to get here.
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John
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I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired 2 WiFi,) SH2 in modem mode with Airport Extreme Router +2 Airport Express's. On VIVID200, Talk Anytime Phone, x2 Mobile SIM only iPhones.