Thank you for reaching out to the Constant Contact Community. It's my pleasure to assist you today.
I'm sorry for the problem you are encountering trying to edit your logo block. It does appear that you are under a partnership with the company whose logo is displaying. If you use one of the saved templates there, it may display that block as locked. You can add an additional block with your logo, or you can Create a New Email Campaign and you will be able to edit that template. If you have further questions please feel free to reach out to us here.
Thank you for choosing Constant Contact. Have a great day!