For those who are on Safaricom, log in, online at
https://selfcare.safaricom.co.ke/ there after, go to PRODUCTS & SERVICES>PHONE BAR
you'll then get a list of all phones you've ever used on your phone, giving the IMEI and the model name, if IMEI is fake, it shall be listed as unknown. You can also get Mpesa statements for the past 3 months etc.
Alternatively, try SUPPORT>INTERNET DATA SETTTINGS, you shall be shown your phone model and number.