If I put my old SIM card into my new iPhone will everything still remain the same?

I just want my number to stay the same and my tariff/package that I pay for every month to stay the same? Need a bit advice, I currently have an iPhone 6s at the moment. I'm not too fussed about keeping all my photos etc cos tbh most of them are on Facebook but as long as my number and monthly package stays the same that's all I'm bothered about

Can call but can't text a person on new phone?

I just bought a Samsung J7 refine through Virgin mobile and there's an issue. One person on my contact list isn't receiving my text messages even though calls go through just fine. This person has an iPhone (I don't know what one) through sprint. Every other contact I've tested has worked with the texting, including other iPhone users. I've tried adding a 1 in front of the number but that didn't help. I also have yet to verify if her texts are able to make it through to me or not.