Partial refunds cannot be enforced, only a full refund.
If you have received an item not as described, you can send the seller a message explaining the fault, and that you are happy to keep the item for a partial refund .
They may or may not agree, and if you are still within 30 days of the item's last estimated date for delivery, you can open a case for item not as described, send the item back if required, at the seller's expense for a full refund.
@marcusgibbons
