MTN 400gb data depleted in 15days

I currently have a home router with mtn for a package of 400gb, loaded ebe month on the 17th. For the past 2 months, my data has been getting depleted at suspiciously early date, for instance, on the 17th of Dec I was loaded with 400gb data, on the 31st of December the data had been depleted. Based on the number of days, how is it possible to consume 26gb of data daily? I'm also notgetting any assistance from the company, I can't get the itemized billing cos it's not the end of cycle yet. 400gb of data cannot possibly deplete in 15days. This is frustrating I'm now stuck with slow connection can barely do anything 😡 Not given an option oof reloading