Clickatell SMS content doesn't print + sign it become empty space , how can I solve this issue

Question

public void sendMessageToRXCustomer(InviteCustomerSMSDto inviteCustomerSMSDto) {
        RestTemplate restTemplateService = new RestTemplate();
        String smsServiceApiEndPoint = env.getProperty("SmsServiceApiEndPoint");
        String txCustomerName = inviteCustomerSMSDto.getTxCustomerNickName();
        String txCustomerMobile = inviteCustomerSMSDto.getTxCustomerMobile();
        long txMobile = Long.parseLong(txCustomerMobile);
        
        //String content = String.format(Constants.INVITE_RXCUSTOMER, txCustomerName, txCustomerMobile);
        String content = txCustomerName+" - +"+txMobile+" wishes to send you an amount of money - to claim the money, you need to register as customer of Mumba Money, using the Mumba Money Mobile app on your phone - Download the app here";
        logger.info("sendMessageToRXCustomer - content: "+content);
        String url = smsServiceApiEndPoint + "&to=" + inviteCustomerSMSDto.getRxCustomerMobile() + "&content= " + content ;
        logger.info("sendSMSToRXCustomer - init - url : "+url);
        restTemplateService.getForObject(url, JSONObject.class);
    }

1.) printed URL in local application : content:

David - +27100200300 wishes to send you an amount of money - to claim the money, you need to register as a customer of Mumba Money, using the Mumba Money Mobile app on your phone - Download the app here

2.) but after sending SMS on mobile it was without a plus sign :

David - 27100200300 wishes to send you an amount of money - to claim the money, you need to register as a customer of Mumba Money, using the Mumba Money Mobile app on your phone - Download the app here