Knowing the telecom workers are on strike, making any form of customer service unavailable, i went on alfa website to activate my postpaid line, login in my account and clicked on activate my line as per the following picture:

Which bring me to the following page requiring a pin code:

Here where it get interesting since i should receive my pin code by SMS, but the genius behind this algorithm forgot that inactive lines DON'T RECEIVE SMSs.

So now I cannot use my line knowing I was paying monthly fees to be able to use it when I need to.
That happens when the people building a system don't actually use the system themselves. It's quite unfortunate.

I would suggest you keep trying to reach them on 111 at different times, try also via live chat. I believe these are your only your only options unfortunately.