Max write length wiith sd_ble_gattc_write

Question

I am using SDK nRF5_SDK_15.3.0_59ac345 with nrf32832. I want to write data from central to peripheral characteristics. I wrote below code: 
 
 ret_code_t err_code;
 VERIFY_PARAM_NOT_NULL(p_ble_lbs_c);

 if (p_ble_lbs_c->conn_handle == BLE_CONN_HANDLE_INVALID)
 {
 return NRF_ERROR_INVALID_STATE;
 }

 ble_gattc_write_params_t const write_params =
 {
 .write_op = BLE_GATT_OP_WRITE_CMD,
 .flags = BLE_GATT_EXEC_WRITE_FLAG_PREPARED_WRITE,
 .handle = p_ble_lbs_c->peer_lbs_db.log_handle,
 .offset = 0,
 .len = length,
 .p_value = data
 };

 err_code = sd_ble_gattc_write(p_ble_lbs_c->conn_handle, &write_params);
 APP_ERROR_CHECK(err_code);
 return err_code; 
 Everything worked fine when I am sending 250 bytes length but for 300 I am getting NRF_ERROR_DATA_SIZE. I set NRF_SDH_BLE_GATT_MAX_MTU_SIZE as 512 and also set MTY using the below code, but still the same issue. Any suggestions? 
 
 void client_int (void){
 ret_code_t err_code;
 ble_lbs_c_init_t lbs_c_init_obj;

 lbs_c_init_obj.evt_handler = lbs_c_evt_handler;

 db_discovery_init();

 err_code = ble_lbs_c_init(&m_ble_lbs_c, &lbs_c_init_obj);
 APP_ERROR_CHECK(err_code);

 err_code = nrf_ble_gatt_att_mtu_central_set(&m_ble_lbs_c, NRF_SDH_BLE_GATT_MAX_MTU_SIZE);
 APP_ERROR_CHECK(err_code);
}