@AIIicin
For the part about transferring a character from one account to another, unfortunately that is not possible to transfer between accounts.
As for the main issue you can try to create a new amazon / twitch account with a different email address, get another code using that secondary email and then apply that code to the account that you want. That would be a quicker option to just create a second account on amazon to just cancel once you get the code.
Otherwise you can try to email "support@swtor.com" to see if they can assist you or call Customer service. I don't think they would be able to transfer the code to a different account. You may need to create a second account on amazon to get a different code but you can try. I know the promotion ends on the 15th of May so you have sometime but I would keep that as an option.
If you wish to call Customer Service, see db woodynz post here with a link to numbers and how to use skype if you have it.
Using skype with that contact is a free call to the best of my knowledge, that number is only available as per the hours listed (Support available from 9.00 CT - 21.00 CT) so need to confirm time zone etc.