Changing the IMEI number of a phone is illegal in many countries.
When purchased, it had an IMEI of all zeroes, and came with a step by step guide to setting the IMEI from my old phone into it.
Apparently that works around phone providers who blacklist or whitelist certain manufacturers.
It's an awesome Chinese $50 android phone.
Because it hasn't passed all the network tests, most mobile networks would block an entirely random IMEI, so they suggest you type in the IMEI from your old phone (as long as it's 4g - if it isn't, they have a support email address you can contact and they'll give you an IMEI that works in your country)
Even the legit Umidigi A3 Pro's (which cost $80, and have proper certifications) have an 'imei change' tool.