problem of activation lock

If you mean "activation lock", neither we (just users like you) nor Apple can help you, sorry, unless you are the original owner and you still have the proof of purchase (receipt/invoice).

Shouldn’t be this case, activation lock can be removed only by the previous owner, with the credentials that were used to activate that iPhone/iPad. Without those credentials, that device is useless to you.

Regards

Giulio

You need to contact the one who sold you the phone and ask her to remove her account.

good luck!