Do you have a copy of the Letter of Offer? If you have, you might as well check for any clauses stating if there is any form of penalty.
Worst come to worst, your loan application may be recorded in CCRIS, and then only will you have trouble getting loans from other banks.

Recently I took loan from PBB half way I cancel the loan then kena Rm2000 penalty (this is excluding legal fees) hehe

Once you applied for your loan it will automatic reflected in CCRIS. Example 3 bank you applied , 3 also approved and it will sure reflected in CCRIS.
No matter you sign or no sigh the LO.
and you can cancel if you dont like the service or package of maybank. as long as u dont sign the loan agreement from lawyer.
the officer sure tell you submit already and cannot cancel + blah blah........ ( u know they need to hit target and earn thier commision so on ) . anyhow, you can cancel.
For more info you should refer back to the S&P lawyer. he can clear all ur question.
just my 1 cent