Take note on the following :-

1) A new USIM card is require to receive LTE signal
2) LTE has been rolled out for data only device i.e. Tablets and Laptops so far
3) LTE for smartphones is not open yet as it's under final provisioning (testing) but you can still acquire your USIM first from any DG center

You can follow these updates and more from DG's twitter page.
Remember to have a LTE device that supports 2600Mhz spectrum as DG only supports that at the moment.