What is the correct Islamic ruling regarding four mobile phones that were purchased from a seller via a website, then the money was returned to the buyer due to his dissatisfaction with the goods, while the buyer was unable to return the phones to the seller who is located in China?

You mentioned that the condition of the website is to refund the money to the buyer if they are not satisfied with the product, and that the website contacts the seller for this purpose. If the website has refunded your money, it is most likely that they have communicated with the sellers and recovered the money from them. Therefore, you should contact the website regarding the return of the phones to them so they can deliver them to the sellers.