Problems with Sim Card and service deceided to move provider not happy!!

I have been with you folks for 2 years now. I realise that I had a problem with the Sim Card for Iphone 6S after actavation of the cell phone. I needed this phone because of my work. So now I have people calling me on that phone and left me messages that I can´t conact them on via email and that´s not the case, They had to send me to the shop Carrefour and they can´t fix it. I need that phone online very urgent you know. So today I decided to move to another interenet provider sorry. I have spent a lot of money you folks seems to have no idea what you are on abouts so now I am moving thanks to your folks. As soon the other providers comes to my house and installation. Where do i have to send your stuff like Modem...receiver and all those stuff?

Regards,

Serge Dardenne