A method and server for establishing a push to talk type service such as push to talk over cellular (PoC). The server receives a message from Client A indicating one or more media types that Client A will accept in defined circumstances in a push to talk type session. When the server receives a message from Client B inviting Client A to establish a push to talk type session for one or more proposed media types, the server determines whether the media type(s) proposed by Client B are acceptable to Client A. If at least one proposed media type is acceptable, the server forwards the invitation to Client A with a list of the acceptable media types. Thereafter the session is established.