Scour the forums, and you will see codes like *#746025625# (SIM CLK) or claims that a simple AT command can change the IMEI.
Disclaimer: This guide is for educational and repair purposes on devices you own legally. Changing IMEI to bypass a blacklist is a felony in most countries (USA: 18 U.S.C. § 1029, UK: Fraud Act 2006). nokia 1208 imei change work
Here is the current state of play for the Nokia 1208: Scour the forums, and you will see codes