The change of address thing seems like a simple case of "meanness" which is not a legal matter.
Signing your name to an IRS check, is another matter. The sheriff could help you with that one.
Oh that's far more than just Meanness. That's tampering with the US Mail and that's a felony.
>>>The change of address thing seems like a simple case of "meanness" which is not a legal matter.<<<
Wrong. Mail Fraud.
banjo joe should talk to the Postmaster at Post Office that handles their mail, and initiate opening a case for investigation.
And forging the signature and cashing a tax refund is indeed another crime - advice to contact local authorities is good...since the IRS is involved, there may also be federal crimes involved - and consulting with the local to banjo joe's area US Attorney's office and/or FBI is advisable.