My MTNChoice 10GB data plan

I have upgraded my contract ***) to the My MTNChoice 10GB data plan, I was getting 80gig a month (40GB Anytime + 40GB Night Express) but for the past two months, my account was only being credited with 60gig, please explain to me where my 20gig x 2months has went because every month your account is paid with no fail. I want my 40gig of data and make sure that on the 17th of Aug 2020 I get my 80Gig.