X509TrustManager unsafe implementation but no such method is used on the code

Question

I got this mail rejecting my new uploaded app on play store

Your app(s) listed at the end of this email use an unsafe implementation of the interface X509TrustManager. Specifically, the implementation ignores all SSL certificate validation errors when establishing an HTTPS connection to a remote host, thereby making your app vulnerable to man-in-the-middle attacks.

To properly handle SSL certificate validation, change your code in the checkServerTrusted method of your custom X509TrustManager interface to raise either CertificateException or IllegalArgumentException whenever the certificate presented by the server does not meet your expectations.

While taking a look on the code I found no such method (checkServerTrusted - X509TrustManager). only X509EncodedKeySpec is used for the In-App Billing.

package util;


import android.text.TextUtils;
import android.util.Log;

import org.json.JSONException;
import org.json.JSONObject;


import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.PublicKey;
import java.security.Signature;
import java.security.SignatureException;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.X509EncodedKeySpec;

public class Security {
    private static final String TAG = "IABUtil/Security";

    private static final String KEY_FACTORY_ALGORITHM = "RSA";
    private static final String SIGNATURE_ALGORITHM = "SHA1withRSA";


    public static boolean verifyPurchase(String base64PublicKey, String signedData, String signature) {
        if (TextUtils.isEmpty(signedData) || TextUtils.isEmpty(base64PublicKey) ||
                TextUtils.isEmpty(signature)) {
            Log.e(TAG, "Purchase verification failed: missing data.");
            return false;
        }

        PublicKey key = Security.generatePublicKey(base64PublicKey);
        return Security.verify(key, signedData, signature);
    }


    public static PublicKey generatePublicKey(String encodedPublicKey) {
        try {
            byte[] decodedKey = Base64.decode(encodedPublicKey);
            KeyFactory keyFactory = KeyFactory.getInstance(KEY_FACTORY_ALGORITHM);
            return keyFactory.generatePublic(new X509EncodedKeySpec(decodedKey));
        } catch (NoSuchAlgorithmException e) {
            throw new RuntimeException(e);
        } catch (InvalidKeySpecException e) {
            Log.e(TAG, "Invalid key specification.");
            throw new IllegalArgumentException(e);
        } catch (Base64DecoderException e) {
            Log.e(TAG, "Base64 decoding failed.");
            throw new IllegalArgumentException(e);
        }
    }


    public static boolean verify(PublicKey publicKey, String signedData, String signature) {
        Signature sig;
        try {
            sig = Signature.getInstance(SIGNATURE_ALGORITHM);
            sig.initVerify(publicKey);
            sig.update(signedData.getBytes());
            if (!sig.verify(Base64.decode(signature))) {
                Log.e(TAG, "Signature verification failed.");
                return false;
            }
            return true;
        } catch (NoSuchAlgorithmException e) {
            Log.e(TAG, "NoSuchAlgorithmException.");
        } catch (InvalidKeyException e) {
            Log.e(TAG, "Invalid key specification.");
        } catch (SignatureException e) {
            Log.e(TAG, "Signature exception.");
        } catch (Base64DecoderException e) {
            Log.e(TAG, "Base64 decoding failed.");
        }
        return false;
    }
}

How can this code be modified to fix the above issue? Need help to fix it.