This is what the resolution (2231) says about Ballistic Missile Activity:
Iran is called upon not to undertake any activity related to ballistic missiles designed to be capable of delivering nuclear weapons, including launches using such ballistic missile technology, until the date eight years after the JCPOA Adoption Day or until the date on which the IAEA submits a report confirming the Broader Conclusion, whichever is earlier.
They can say what they want to say. Called upon means requested it doesn't mean any obligation. And it is related to types of missiles that can deliver a nuclear warhead.
They can't praise Iran for doing this you know and they can't say nothing. So this is what they say. The Resolution that bans Iran from performing any activity related to ballistic missiles is 1929 in paragraph 9:
9. Decides that Iran shall not undertake any activity related to ballistic
missiles capable of delivering nuclear weapons, including launches using ballistic
missile technology, and that States shall take all necessary measures to prevent the
transfer of technology or technical assistance to Iran related to such activities;
However, resolution 1929 along with a bunch of other resolutions were terminated by resolution 2231:
(a) The provisions of resolutions 1696 (2006), 1737 (2006), 1747 (2007), 1803 (2008), 1835 (2008), 1929 (2010) and 2224 (2015) shall be terminated;
So the language about restricting Iran's ballistic activities has changed from a very firm obligation in resolution 1929 to a request in resolution 2231. Meaning Iran has more freedom after resolution 2231 to perform ballistic missile activities than before it was approved.