The recommended way to tell whether a user is enrolled in Bill Pay would be to check the isEnrolled flag that comes in with billpay capabilities on the UUX platform. Here's a code example for how you would request that object through Tecton.

await this.tectonSDK.sources
  .requestPlatformData({
    route: `mobilews/refreshCapabilities`,
    method: "GET",
  })
  .then((response) => {
    this.billPayRights = response.response.data.isBillpayEnrolled;
    this.userId ...