The 699 is a TMobile phone, so it doesn't have to be unlocked (but it's okay if it is). Call the customer service number for Walmart's Family Mobile (try 1-877-308-9621). Have the phone off and the SIM in your hand (so you can put the SIM back in). (There should be a number on the SIM. If not, there are apps in the Play Store that you can install (via wifi) that will give you your SIM's number.) Also have the phone's IMEI handy. (It's the "Dec:" number on the label under the battery.
Tell them that your phone was stolen and that you're replacing it with a different phone with a different SIM and they'll either enter the new information or switch you to the department that does it and they'll do it. It might take up to an hour before your local tower actually gets the information and your phone works. (They may tell you to wait 24 hours. It's possible that it could take that long - not likely any more, but possible.)
You'll also have to set the APN information. Go to Settings/Connections/More networks/Mobile networks/Access point names. Go to the one in there and see if it's correct. If not, add one, label it whatever you like (Walmart, for instance) enter all the information and save it. Then delete the other one. (The phone will work without this but data and MMS won't. until you do this.)
See
https://www.myfamilymobile.com/Supp...x?device=a649a78a-bd94-457c-90a3-7c8b7ac7b1f8 for more information and
https://www.myfamilymobile.com/Supp...x?device=eab765d2-eb35-494b-94d2-19890ec46c77 Verify and update the APN settings #7 for the APN settings. (#12 means long-press the power button and select Reset. It may not be necessary, the phone may work as soon as you save the APN.)