We got you covered! This can actually be changed in the voicemail settings but that is gonna be pretty tough to do if you don't speak Spanish.
If you want to try and do it yourself, you can dial 123 from your device to access your voicemail box. After you messages have played (if you have any) press 4 and then press 7 for English.
If you are unable to get your mailbox changed with this route, you can call our tech support team and they can change it for you on the back end