There are many things which can cause this and the fix will depend on how the content that is freezing is being delivered to you. If it is a Freeview channel like BBC1 or ITV then it may be an issue with your ariel if you are using one. If not or if the freezing continues on internet channels which you pay for or the apps that suggests a poor connection between your TV box and the broadband hub.
If you are running a cable directly been the two boxes then try to plug the cable into a different ethernet port or swap the cable over with another. If as I suspect you have connected wirelessly then the boxes may be too far apart or being interrupted by other factors. If this is the case then EE can check these out and look for a different solution wither a wired connection if they are close or through adapters they call power line adapters which when hooked up sends the signal through the electrics (Providing the two sockets are on the same ring main / fuse box) - I had a similar problem with my TV box upstairs and this was the fix for me.
This is presuming there is no underlying general broadband connection however you would likely be seeing issues with other devices. I would contact EE directly and speak to technical support who will be able to check all this out and advise specifically.
There are a couple more possibilities such as the HDMI connection between the box and TV or some of the picture quality settings but these are less likely based on how you have described it.
