Thirsty.
I hear your anger but anger is not a good policy.
You have the letter that they will accept interest only.
1. Be careful that this is not just for a fixed time.
2. If it is open-ended then happy days for you !
3.Do not then get stressed over (demands)
4. If things improve chip away at the principal as rates in time must rise.
If it is not open ended for ever(I don,t think it will be) study carefully what you can do and work from there.
Make sure you do not drift outside the MARPS process.