Boosters for prepaid plans

I am massively confused by my account right now. Last summer, I got a text saying that the monthly fee was going from $15 to $18 on my prepaid plan, which was for unlimited text and 100 minutes of Canada wide calling. I was very happy with that plan because I make and receive very few phone calls and just bought data boosters periodically as I used them up. But a few months later, I tried to buy an additional data booster and was told - by a HUMAN agent, not an AI - that there were no boosters any more and that my $18 plan now gave me UNLIMITED calling (and I think texting) but only a very limited amount of data - 250 MB or thereabouts - and that I’d have to pay more if I wanted more data. I told him to leave me with that plan for the moment so that I could see if it that was sufficient for my modest needs. 

Today, I went into my account and noticed that it was back to 100 minutes of calling and there were a variety of boosters again; my data was almost exhausted so I bought another data booster of 3 GB for $15. But then I noticed that there was a notation of 30/30 and found that this meant that whatever I hadn’t used in 30 days would be lost to me. I know I will never used up 3 GB in one month so asked the AI about this and it gave me contradictory information that implied that unused data would indeed be forfeit after 30 days AND that it would roll-over until used up.

Right now, I am completely baffled about what’s actually going to happen! Can someone enlighten me? 

Again,, let me stress that I’m a PREPAID customer, not a MONTHLY customer.  I’ve got a bad feeling that the human who helped me with my account mistook me for a monthly customer and gave me completely inaccurate information. I’m hoping that I can continue buying data boosters that roll-over until they are used up. But if I’m mistaken, I want to RETURN the 3GB  booster and buy a much smaller data booster that more closely reflects what I’ll actually use in a month.