【求助】用AT指令发送AT+COPS查询运营商状态出错

[浅蓝Light_Blue]

如题，我用AT指令发送给短信猫查询卡的运营商状态

我发送SendAT("AT+COPS")给短信猫，返回的是AT+ERROR

但是我的卡没问题没欠费，短信猫信号也正常

可以正常的收发短信，但是差不了运营商状态

而且发送SendAT("AT+CPIN")返回的也是AT+CPINERROR

请大神给检查一下是什么问题啊，下面是SendAT()的代码

        public string SendAT(string ATCom)
        {
            string str = string.Empty;
            //忽略接收缓冲区内容，准备发送
            this.sp.DiscardInBuffer();
            //注销事件关联，为发送做准备
            this.sp.DataReceived -= this.sp_DataReceived;
            try
            {
                this.sp.Write(ATCom + "\r");
            }
            catch (Exception ex)
            {
                this.sp.DataReceived += this.sp_DataReceived;
                throw ex;
            }
            try
            {
                string temp = string.Empty;
                while ((temp.Trim() != "OK") && (temp.Trim() != "ERROR"))
                {
                    temp = this.sp.ReadLine();
                    str += temp;
                }
            }
            catch (Exception ex)
            {
                throw ex;
            }
            finally
            {
                this.sp.DataReceived += this.sp_DataReceived;
            }
            return str;
        }