Check with ur mobile, probably it has the feature to block certain numbers.
Most of the phones have sum feature called close active group i.e when activated, only the phone numbers u enter in the settings will be allowed and outsiders call will be barred automatically.

If ur phone got none, check with Qtel by calling 111 and asking whether they got call barring service.

note; someone pointed out call diverting is free,in fact its not if the person ur diverting to picks up the call