False promotion

Subscribed fixed wireless and have choosen 1 month free data or 100 Gb i.o. Huawei router. Got only 76 Gb as they claim subsciption 8 th. of month and they calculate a pro-rata amount. This is NOT specified in offer. This if you subscribe say the 30 th. of the month, you get only a few Gb. i.o. The Huawei product.