I just activated my new iPhone and transferred all my data/apps Frim my old iPhone to my new one. However my cell service is still on my old phone. How do I transfer?

Take the SIM card out of the old phone and put it in the new phone. See→Remove or switch the SIM card in your iPhone or iPad - Apple Support or watch this companion video:

You can also contact your carrier and ask them to activate the eSIM in your phone.

i have got an iPhone 11 and put my sim from my iPhone 7 into it but i can't make or accept phone calls ?

Then you need to contact your carrier to resolve the problem.