let me ask you this, if you haven't used all your data allotment and not throttled yet, if T-Mobile or any other carrier will tell you, you have whatever GBs to use up to 4G LTE speed, what does that mean? it means that it could be from 0 SPEED up to whatever speed the LTE will provide you in a certain area at a certain time on a certain day.
Now what is the LTE speed according to your specs???