I need help with Dispatch within the context in React

Question

I made a resquettes to save an image in our API but I’m having problems in the Dispatch of this resquet and worked:

const trocarAssinatura = async img => {
    dispatch({ type: actions.SET_LOADING_ASSINATURA, payload: true })
    const data = new FormData()
    data.append('assinatura', img)
    data.append('fornecedor', maquinadeestadosstore.getIdEmpresa())
    try {
      const res = await Api.post('/portal/proposta_assinatura/', data)
      dispatch({ type: actions.SET_ASSINATURA, payload: res.data.assinatura })
      
    } catch (err) {
      AlertaError('Erro ao enviar assinatura.')
      console.log(err)
    } finally {
      ToastSuccess('Assinatura enviada.')
      dispatch({ type: actions.SET_LOADING_ASSINATURA, payload: false })
    }
  }

In the case Dispatch({ type: actions.SET_ASSINATURA, payload: res.data.signature }) is not working. I migrated this function from Mobx to Context and mobx was like this:

@action handleAssinatura = img => {
    this.loadingAssinatura = true
    const data = new FormData()
    data.append('assinatura', img)
    data.append('fornecedor', maquinadeestadosstore.getIdEmpresa())
    Api.post('/portal/proposta_assinatura/', data)
      .then(res => {
        this.assinatura = res.data.assinatura
        ToastSuccess('Assinatura enviada.')
      })
      .catch(err => {
        AlertaVermelho('Erro ao enviar assinatura.')
        console.log(err)
      })
      .finally(() => {
        this.loadingAssinatura = false
      })
  }

Can someone help me?