how come I can make calls but cant get on a network or see contacts?

I just put my old sim card in my new galaxy s7 but cant get on net. It has been suggested that my phone is locked but then how come I can make and receive calls and text even with Wi-Fi off.

Master Of Puppets2018-08-11T18:21:27Z

If your phone is network locked to a different carrier, it wouldn't have accepted your SIM card.

More likely than not, you'll need to input the APN settings for your carrier on your S7. You'll need to find the settings for your specific carrier.