bad experience

last week and today my data was flucuatimg in and out  i contact at&t via phone call and text messages they changed the provisions  on my phone and the updated the phone but it still doesnt work well  i recontacted at&t today thru texting  and i was blown off after i gave the rep my imei number  and i told them how at&t tried to fix my phone  what else can i do to get at&t to fix my phone and how do i contact corporate ?