keep getting errors (LINK IN BODY)

https://forums.att.com/t5/Account-Features/Can-t-change-call-forwarding-settings-quot-Connection-problem/td-p/4849225

i'm having the same problem as this person, who was instructed to send a private message...

but you do not allow private messages anymore?

so how do i get help on this issue?

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== Details ==

a. If I try to set call forwarding through my Android phone's Phone Settings (Phone > Settings > Calls > Call forwarding), it says "Unexpected response from network"
b. If I use the MMI code "**004*1235556789#",  I receive the error message "Connection problem or invalid MMI code."

=== Background ===
I was able to change call forwarding settings with no problems until I received a new LTE SIM card (no change in phone). That is, on this phone I was able to change call forwarding settings and they would stay, but when I got a new SIM card with LTE support my call forwarding settings were reset and I can no longer change them myself.