I started my Virgin Media broadband account 11/11/2020 and was supposed to receive a £50 Amazon Voucher, which I have not, as of 19/04/2021. A phone number via which I could contact Virgin Media would be helpful.
This webpage has a tab "Voucher Offers" which explains the timescales, procedures and contact details involved when applying for free gifts when the original contract was placed directly via the Virgin Media website, without going through any third party. virgin-media-free-gifts
The Service you do for others is the rent you pay for your room here on Earth - Muhammad Ali
Further to the advice from newapollo above - if the faq's don't help and you have confirmation of the deal you signed up for that shows the deal including the voucher then please let us know, we'll try our best to help further.
I do not appear to have any documentation which mentions the voucher but I am sure that Virgin Media will have a record of it. The deal was available via 'Broadbandchoices.co.uk' in November 2020 but I actually made the arrangement, including the voucher, when one of your colleagues telephoned me.
I trust that Virgin Media will honour this agreement with some urgency.