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I'm not sure whether that issue is related to Fido or not. Truecaller uses various sources to obtain their CallerID. It uses user-profiles and public partnerships to identify the name connected to the number. They also have community sourcing for names (see here). It's possible they have the name associated with your number's previous owner. You might need to contact Truecaller to correct that information. Alternatively, if you register for the app, you should be able to choose how you want your CallerID to appear.
Does the CallerID / Name Display show a different name when not using Truecaller?