Network locked sim card inserted

[Poorwhiteman]

I have a straight talk phone j7 sky pro and I am switching my service to another provider and so I check to make sure that my phone was compatible and it was so I put the new sim card in and I had to change the APN  so 

I did that and then I took the sim card out and put it back in and turned the phone on and it read network locked sim card inserted so I'm trying to 

find out what to do now

[will13am]

@Poorwhiteman, I am a little confused here.  You were able to use the SIM card once in the phone and then after entering the APN settings, taking out to SIM card and rebooting the phone, it's not working anymore and reporting that the SIM card is network locked.  Is this phone unlocked?  You mentioned that it's from straight talk.