Help regarding a section 21

Hi thank you for allowing me to join iv been served with a section 21 notice a virgin media want nilley £400 disconnection fee non of this is my fault or choice and I feel im being penalised i don't have the finances to pay this aswell as becoming homless this is added stress and anxiety i don't need right now please i need some help and advice asap they have also disconnected my services without me even confirming that I was happy to disconect and pay the fee help me please