SIM activation issue

I ordered a new sim with contract for my son, it's  an o2s contract with a new phone. His birthday is on Thursday so I started the activation setup last night, but there's a problem. It won't activate, despite it saying "Dein SIM ist schon aktiviert.."  can the o2 experts have a look what's going on for me please? It looks to me, based on what is showing in my o2 app, and from the evasive response of the o2 person I spoke to today, that something was setup or ordered incorrectly, and I'm worried that the birthday present wont be ready for Thursday. Although I  ordereda new contract,  there was no phone number on the Sim card like there should have been so I'm worried I was sent a spare sim or something like that.  I am sure there was a mistake at the o2 end, help please!