From India, Hyderabad

Irrespective of you completed the notice period, handing over formalities, as for employer is concerned if it is not approved by employer then obviously he will send warning letter only. Instead of leaving without information you should have negotiated with your employer and should have arrived at some amicable date based on mutual convenience. Though you are right in your Act future employer will not trust your statement and they will expect proper relieving order only.
From India, Madras