Bachmann DCC with MRC Tech 6 6.0

[ranveal]

I have 2 brand new Bachmann locos I purchased from an online retailer, both run fine, but I cannot change the default address from 3 to another address (1-6) that the Tech 6 will operate.  MRC tech support insists that it is not an issue with the Tech 6 6.0, but an issue with the Bachmann decoder.  They even sent me a work-around for Tsunami decoders which involves changing the 2 digit address to a 4 digit by changing CV's, and that procedure did change the address form 3 to something, but I could not reprogram the address to a 2 digit.  My locos are the 70 Ton switcher & a GP35.  Can you tell me something to try to change the default address to anoth 2 digit address?  Thanks so much.