このようにしてみてください...
TLSentCode sentCode;
try {
sentCode = api.doRpcCallNonAuth(new TLRequestAuthSendCode(phone, 0, 5, "your app id", "en"));
} catch (RpcException e) {
if (e.getErrorCode() == 303) {
int destDC;
if (e.getErrorTag().startsWith("NETWORK_MIGRATE_")) {
destDC = Integer.parseInt(e.getErrorTag().substring("NETWORK_MIGRATE_".length()));
} else if (e.getErrorTag().startsWith("PHONE_MIGRATE_")) {
destDC = Integer.parseInt(e.getErrorTag().substring("PHONE_MIGRATE_".length()));
} else if (e.getErrorTag().startsWith("USER_MIGRATE_")) {
destDC = Integer.parseInt(e.getErrorTag().substring("USER_MIGRATE_".length()));
} else {
throw e;
}
api.switchToDc(destDC);
sentCode = api.doRpcCallNonAuth(new TLRequestAuthSendCode(phone, 0, 5, "youa app id", "en"));
} else {
throw e;
}
}