I'm sorry to hear your phone line isn't working at the moment. I'd certainly like to get this looked into for you.
To be honest I'm not sure who this junction box belongs to as there's nothing identifiable on the box. I've managed to run a few checks on your line however and think it best if we arrange for one of our engineers to come out to the property take look at this issue. If the box is the cause of the issue then our engineer will be able to sort this for you.
I will drop a PM to you shortly (purple envelope top right) so we can discuss this further.