When I switch the email account the signature is not swithed

Question

I use several diferent email accounts with Thunderbird. I want the signature to switch once I change the account I'm answering from. Yesterday Thunderbird asked me how it should behave when I switch the account I'm answering from. I said 'remember my answer' and than pressed the wrong button. How can I undo this (without reseting all my settings)

Answer 1

Ok. I seems I did not explain very well. I do not use any add-ons
1) I use several diferent email account - each one configured with a specific signature / f.i. [email protected] / [email protected]
2) Sometimes I receive an email in [email protected] but I want to answer from [email protected] so the conversation goes on with me - instead of entering into general...
3) When I switch between the account I'm answering from (general-->myname) the signature should switch also from general --> myname.
4) This generaly worked but last time I did this Thunderbird asked me how it should behave --> if it should stick with the original signature from the original account I received the email (general) - OR - if it should switch to the signature of the account I just selected (myname)
I checked "remember my answer" and than hit the button that means DONT CHANGE SIGNATURE IF YOU CHANGE EMAIL ACCOUNTS.
Thats what I'm trying to undo.
Thanks for any help.