1. Field Mode: *3001#12345#*: Type *3001#12345#* into your phone’s dialer and then press the green call button to access “Field Mode,” which can give you access to info about local networks and cell towers.
2. General Test Mode: *#0*#: I could only get this to work on Android. But this prompts a library of different phone operations, which could be operated with a single push (e.g. Sleep, Front cam, vibration
3. Display your IMEI: *#06#: Here’s a code which I found out does not work with Verizon on an iPhone, but I could make it work after switching to a T-Mobile SIM. To access it, type in the above code, and then the green call button to prompt your IMEI number (or your International Mobile Station Equipment Identity number, but you already knew that).
4. Check Your Call Forwarding: *#67#: This code allows you to check which number your phone is currently forwarding calls to when you’re busy or reject a call. On an iPhone, you can change this number by going to Settings > Phone > Call Forwarding
5. SMS Message Center: *5005*7672#: This code will tell you your SMS message center number
6. Activate Call Waiting: *43#: This code will activate call waiting; you can deactivate it by entering #43#
