Thanks for joining us on the forums and a warm welcome to the community
I'm happy to see that since you posted that the engineers have been out to correct the missing box and cable issue and that the credit is also showing as has been agreed.
Just so you know it is possible for us to apply credits to pending installation accounts that have not yet been connected which we can do providing the services are going to be connected in the near future.
Bills generate based on the initial date the bill is set for that is in a cycle set by the original connection date so this may have been set in motion when the services were sent to you to activate, and that is why my colleagues applied a credit for you, to cover you for services additionally on top of the promotional credit you have mentioned
To check this out on your billing you should be able to see this by logging into My Virgin Media where you can check out your bill and the credit amounts showing.
Additionally if you get in touch with the teams via 150 or 0345 454 1111 or via Webchat they will be happy to look into the billing side of things for you once they clear DPA with you where, if you pay by Direct Debit with us, further adjustments can be made to any pending payments that may be showing for you if this is not quite right still.