air travel – Refund for a cancelled return ticket

I bought a round ticket with Kenya Airways, and used the first ticket,
but the return flight was cancelled due to Covid-19.

the airline offered an open ticket that will be valid till June 2021, and that they can offer a refund only after that date.

I already booked another return flight, and have no need of the open ticket.

Is there any way for me to get the refund without waiting a year?
Can I dispute the charge with the credit card company?