Should have been a little more specific & stated Peplink forum.  Other sites which may assist you in locating data plans are ltehacks.com, howardforums.com, Mobile Internet Resource Center has a list which is pretty complete, Mobile Must Have has an AT&T reseller they use if you buy equipment from them & I suspect there are others.  I believe there are several members on this forum who use the same device you are considering acquiring, or other Peplink products, who have 'uncovered' ways to acquire sufficient data to use their products.
In defense of Peplink, I suspect most of their devices were developed for commercial markets which typically have dedicated IT support people.  They are providing the same level of support on securing internet connectivity as a company like Arris, CISCO or NetGear provides you when you select one of their products for use in a permanent physical location.  Essentially, you find what's available on you own.  Probably don't like that answer, but, you either do it yourself or pay a systems integrator to do it for you.
Do you have any feel for how much data you will consume in a month & what you will do with it (as in transmit & receive over the internet)?  Is it time sensitive, can it be compressed, does it need to be secure & those type of things?  You may find your data needs are not as high as you think they are.  Then again, you may find they are much higher than you anticipated.