Is it obligatory to return the money to the global website after repairing the vacuum cleaner for which they sent the price, but the paid amount was not withdrawn?

You have no right to this money. It is obligatory for you to return it to its owners. It is not permissible for you to combine the price and the item, nor to consume their wealth unjustly, due to the Almighty's saying: "Do not consume your property among yourselves wrongfully, but let there be trade [involving mutual consent] among you," and due to the Prophet's (peace and blessings be upon him) saying: "Indeed, the wealth of a person is not lawful except with his willing consent."