RESTful command variable

Hi, everyone!
I have an external boiler, and i get target temperature from it. It works well. Like this.

   zont_target_temp:
      value_template: '{{ states.sensor.zont.attributes.devices[0].io["last-boiler-state"]["target_temp"] }}'
      friendly_name: "target_temp"
      device_class: temperature
      unit_of_measurement: '°C'

I want to make a button to inscrease temp to 1 degree. I made REST_command with variable “temp”. Like this

zont_temp_target:
   url: url_termostat
   method: POST
   headers:
     x-zont-client: !secret zont_client
     x-zont-token:  !secret zont_token
     Content-Type: application/json
   
   payload: '{
     "device_id": device_id,
     "thermostat_ext_mode": 5,
     "thermostat_ext_modes_config": {
     "5": {
     "active": true,
     "hidden": false,
     "name": "Hassio",
     "zone_sensors": {"1": null},
     "zone_temp": {"1": {{ temp }} }
        }
       }
     }'

And also I made a button in loveace.yaml like this:

- type: button
    name: zont_plus
    show_name: "false"
    icon: mdi:plus
    icon_height: 20
    action_name: Heat
    tap_action:
       action: call-service
          service: rest_command.zont_temp_target
             service_data: 
                 temp:  "{{ states('sensor.zont_target_temp') | int +1 }}" '

And it doesn’t work (nothing happens). The problem is in
temp: "{{ states('sensor.zont_target_temp') | int +1 }}".
When I change it to temp: 14 (16,17....) it works properly. Where am I wrong? Could you help me please someone…

Not sure if it’s in the post only, but you have a superfluous single-quote at the end, here.

Sorry. It’s my mistake, while copying the code here. There’s no a single quote. HA doesn’t show a mistake here.

Hello! Tell me, did you manage to solve this issue?
I’m trying to do the same right now