module.cs

public class Module : IModule
{
  public void Initialize(IServiceCollection serviceCollection)
  {
      //register CustomerOrderService in DI first
      serviceCollection.AddTransient<CustomerOrderService>();
      //Register decorator for original CustomerOrderService
      serviceCollection.AddTransient<ICustomerOrderService>(provider => new MyCoolCustomerOrderService(provider.GetRequiredService<CustomerOrderService>()));
  
  }
}

MyCoolCustomerOrderService.cs

using System;
using System.Collections.Generic;
using System.Text;
using System.Threading.Tasks;
using VirtoCommerce.OrdersModule.Core.Model;
using VirtoCommerce.OrdersModule.Core.Services;

namespace VirtoCommerce.OrdersModule.Data.Services
{
    public class MyCoolCustomerOrderService : ICustomerOrderService
    {
        private readonly ICustomerOrderService _originalService;
        public MyCoolCustomerOrderService(ICustomerOrderService originalService)
        {
            _originalService = originalService;
        }

        public Task DeleteAsync(string[] ids)
        {
            return _originalService.DeleteAsync(ids);
        }

        public Task<CustomerOrder> GetByIdAsync(string orderId, string responseGroup = null)
        {
            return _originalService.GetByIdAsync(orderId, responseGroup);
        }

        public Task<CustomerOrder[]> GetByIdsAsync(string[] orderIds, string responseGroup = null)
        {
            return _originalService.GetByIdsAsync(orderIds, responseGroup);
        }

        public Task SaveChangesAsync(CustomerOrder[] orders)
        {
            //TODO: Add validation logic here
            return _originalService.SaveChangesAsync(orders);
        }
    }
}