stranded in the transit area in istanbul

not sure how if you have a two-part ticket (South Africa to USA via Istanbul), Turkish Airlines can let you board the first leg but then refuse you access on the second and leave you stranded in the transit area without a visa or flight out. at time of writing I'm not sure how this works out as their call centre won't help and the staff in departure are indifferent but it's several thousand rand lost and horrific being in limbo in a foreign country