Have I messed up?

Durban

I am new to stoozing

I have a balance on MBNA card of around £5000 at 0 percent for about another year. I pay minimum amount and have the £5000 in a savings account. 

I have now taken the 0 percent fee offer of 21 months at 6.9 percent and MT around £7500 today on the same card and immediately did a BT of the same amount from another 0 percent card. 

I thought this would clear the MT and leave my £5000 balance at 0 percent intact 

However , I have now been reading that this may not be the case and I may have jeopardised the 0 percent on my existing balance of £5000 and I should have done this with no balance outstanding and I may now be paying 6.9 percent on the £5000 instead of 0 percent 

is this correct and should I now pay off that £5000 asap or will my 0 percent still stand until the expiry of that offer 


Thank you