The imprisonment may be up to 18 months. Usually, when the judge decides that there is no prospect on deportation, you must be released. This is often after 6 months, but can be extended with 12 months maximum when the DT&V blames you for not cooperating on your own deportation. In prison you have the right to obtain a lawyer and medical support, although in practice the medical care is often not sufficient. You can receive papermail, and visitors. Then you should ask for permission and mention the name and date of birth of the person who wants to visit you. You get a weekly allowance, which you will need to buy extra food or to call.
There is a hotline for people in immigrationdetention. If you have complaints about your treatment in detention you can contact 0800 3388776 (it’s for free for people in detention) More information: www.meldpuntvreemdelingendetentie.nl (in dutch).