Eir contract cancelled and now still being charged

Hi All,

I couldn't contact Eir customer care... As I heard it is normal situation... So I have sent my resignation to them via post. My contract was due to May 2019. I have received text saying they confirmed my resignation as follow:
Reminder: As you cancelled your eir service(s) you must return all eir equipment to us within 30 days of your cancellation date to avoid a charge on your final bill. See eir.ie/equipmentreturns. If you’ve already returned your equipment you can ignore this message. From eir ...
It was on March 2019.
I understand I have received another bill as it was last month of my contract but now I was charged again!!! 57 eur and chat agent said I have active account since 15/03/2019 for another 10 months!!!
They took money from my account and I don't know what to do ?!
Please help me what can I do to solve this situation!