If you did not change the number the new Sim Card will replace the old.
Sometimes it takes hours for the change to be active.
Ask to your Telefone company how long it will take and if you should keep the phone not connected to the service.
Sometimes there are also problems. In Italy few month ago I had to wait 7-8 Days for a system problem during the change of my Sim (Vodafone).
BTW, they told me several times: it works, just wait few hours... just wait until tomorrow ... and so on.
People of telephone companiet like to think they are right and you are stupid.
It takes time and nerve to convince them to go a step up in competence and solve your problem.