How do icq messages come through sms?

Question

MTS

Good day. The point is this.
I gave one friend my second, unnecessary ICQ number and password from it to use (he was too lazy to register, and I needed to correspond with him from the phone.)
After all, SMS is much more expensive than ICQ.
As a result, I was visiting this person, and as a joke I sent him a message while he was in another room - "what are you doing?" - the answer came "I'm in Ukhta, at work now." I fell into a stupor. Stole the number - I thought. At this time, my friend came from another room, I asked him if my messages had not come to him in ICQ for a long time - it turned out that for a long time.
Began to understand. It turned out that my friend answered mefriend, to whom I never gave this ICQ. Yes, he never used ICQ - everything sits on VKontakte. He does not recognize any messengers, it is easier for him to write SMS.
And now the magic:
I asked - how did you get into this ICQ? Where did you get ICQ, number and password from it?
He just sent me the following screenshot in response:
That is, he has no idea why he receives SMS with my messages from ICQ, but when he responds to incoming SMS to the short number from which they come, the messages in response are delivered to me in ICQ. Moreover, his contact is always online.
There is no point in talking about the hijacking of a number by this person - the person is completely not technically savvy, and he does not need it at all.
How is it at all? Maybe someone knows?

Answer 1

download.icq.com/download/icq/features/sms/ru
www.icq.com/support/icq_8/sms/rate/ru