Hello KAZFZ,
Welcome to the community!
I know the 2500 call forwarding minutes are included in the Voicemail Value packs (see here, under Voicemail). At one point, some of the features included in the value packs were available as standalone add-ons, even though they did not appear on the website. You would need to enquire whether that particular feature is available standalone.
You should note this forum is community-driven and not intended as a venue for customer services. If you would like to query about the availability of the call forwarding add-ons, you would need to contact customer service for verification. In addition, they can also be contacted via Live Chat, Facebook, or Twitter. Those methods can be accessed via the contact page posted above.
Hope this helps 😀
Cheers
