I take college courses online so my data usage is high during the term, and low when between terms. I need more than an extra gb during term, but not even the 18 I have otherwise. Is it okay to simply go from the 18 to 25 then back to 18 or even down to the 10 plan often as in at 6 to 8 week intervals, or will that cause problems in billing? I understand there are no fees for changing plans, but what about administrative and system function hassle?