Turkish Airlines Misled Me with Primefly Ticket but Applied Ecofly Refund Rules

I bought an IST-BOG round-trip international ticket for my wife’s sister, with a return date of 16.01.2025. Turkish Airlines operated the flight from Colombia to Istanbul. I purchased the ticket under the Primefly option to ensure flexibility. However, when I tried to cancel the return ticket before the flight date, they claimed it could not be canceled since the outbound flight was already used. They said if we wanted to keep the return flight open, it would be considered a missed flight as of 16 December, requiring an extra $260 fee plus a $15 service charge. When I requested a cancellation, they said the refund would follow Ecofly rules, offering only ₺2,500 for a ticket worth ₺57,000. I specifically purchased the ticket under Primefly for free refunds and changes as advertised, verifying these features multiple times during booking. How are we expected to know Turkish Airlines' internal rules if even their call center staff seem uncertain? An employee even forgot to mute their microphone and asked a colleague if the full amount should be refunded. The explanation I received was: "Since your outbound ticket was Ecofly and your return ticket was Primefly, Ecofly rules apply." I asked where this rule was written, and they just repeated, "These are the rules." If even Turkish Airlines staff are unsure of the policies, how can passengers be expected to know? Why sell a Primefly ticket if Ecofly rules override it? They asked me to fill out a feedback form, promising a response within 2-7 business days. We purchase tickets online to save time, not to encounter such complications. Turkish Airlines is a reputable company that shouldn’t resort to such confusing policies. I have a 3-month-old baby and cannot afford to lose ₺55,000 (about $1,600) due to unclear terms. I will pursue all my legal rights and hope to find someone who can resolve this issue.