It is possible to change your contract from one person to two people. This requires a charging fee of €45. To change your contract, simply head over to your online account.
Please note that, if you want to change your contract from one person to two people, you have to be living in a residence that is suitable for two tenants. Not all residences allow two people to live (i.e. studios). Hence, it is a must that you live in a residence that can allow two people to live in order to successfully change the contract.