I ended up sending a second email to them and finally they replied, twice!
Thanks for contacting Just Mobile, We value this opportunity to assist you. *
You can attach our "Go button" to any hard case of your iPhone 4, please find attached file for reference.
With the smart "Go button" you can still use our Xtand Go even if you change to another phone in the future.
Meanwhile we're developing a new bracket for iPhone 4, If you wish to use your Xtand Go with naked iPhone 4
please check out our website later.
Many thanks for your continual support to Just Mobile.
Many thanks for contacting Just Mobile, for some reason your e-mail went to our spam folder
and we just see it right now. We do apologize for our late response.
May I know your opinion with iPhone 4 on the Xtand? We tested it and found that Xtand can*
hold it firmly in place. However in newer shipment we'll create an new bracket for iPhone 4,
Just Mobile is committed to deliver 100% quality.
If you have any question please don't hesitate to contact us.