I don't fully understand what meaning you assume by "I don't negotatiate!"
But "I am not discussing it" or "Out of discussion" - I think the best Russian translation would be
- Это не обсуждается!
1. вести переговоры (с кем-либо о чём-либо) - to conduct negotiations (with somebody about something), this one is used for official negotiations between countries, governments, or between companies.
2. обсуждать (что-либо с кем-либо) - to discuss something with somebody - a commonly used verb, usually implies a peaceful calm discussion
3. дискутировать (о чём-либо) - to discuss, to debate something - it usually implies there is a variety of opinions on some subject
4. потолковать (о чём-либо) - to have a talk about something - this verb belongs to the colloquial style, and I think it is more common among the older generation