With an issue date of 28th November and having submitted your AoS in a timely manner, you had until 4pm on Friday 27th December to submit your defence. Since that time, the claimant is able to request an automatic CCJ against the defendant.
I suggest you immediately (right now) submit the defence, any defence, in the hope they have not already issued the CCJ. We don’t normally suggest using the MCOL for submitting a defence but you are in a race against time.
Luckily there was a similar case a day or so where I provided a suitable defence for use on MCOL and I will provide it here as soon as I find it.