Synchrony Bank Credit Card Complaint

Synchrony Bank Credit card department,

Credit card protection / Debt protection California

On -/-/15 someone contacted synchrony bank ( walmart ) and requested a change of address to florida and had my credit limit changed from $400.00 to $3400.00. No one from synchrony questioned theses changes, called me to verify or anything. This person made a lot of charges. on -/-/15 I recevied a letter from synchrony asking if these changes where made by me. I know mail only takes about three days to get -. Upon receipt of this letter i called and was told what had happened and that i was not responsible for the charges. they gave me a new credit card number but because they were unable or unwilling to tell him how they allowed this to happen in the first place i had the card canceled. On -/-/15 they mailed me a fraud letter and i received it on -/-/15. I want a full explianation as to how my security with them was breached and why i was not called the day for this major change was requested. I also want a written apoligy for the hardship this has caused me.