I think Microsoft has finally found solution as I can now download without interruption, no more error c101a006. The problem actually is from Xbox account so this is what you do.
1) go to settings, language and make sure you note the region/country on your phone
2) login to xboxlive.com with your account details
3) at the bottom right corner, there is a new menu option to move your region. Click on this and make sure your region/country details matches with the one on your phone.
4) A pop to accept new Xbox terms and conditions will appear, accept the terms.
5) confirm all other details...eg date of birth to be the same as in your Microsoft account (hotmail, live or outlook)
6) Reboot your phone and enjoy unlimited download and the fun of a great smartphone
note: I have tried this and it worked on my phone.