I take it that by harassment you mean some chap/chapess phoning you up to try and flog you VM stuff? Just have a delve in your My Virgin Media Settings, and somewhere ("My account" ?) there's a setting for marketing preferences. Turn it off, and after a few days the calls should stop.
As for loyalty, that counts for nothing. You either accept that and pay VM's full-fat tariff, change your ISP, or you try and blag yourself a better deal. Be aware that new VM and other large ISP contracts and changes are all 18 month fixed terms now.
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