TDI addresses this question on its website: https://www.tdi.texas.gov/health/faqs.html
TIC §1501.108(d) does not permit an issuer to unilaterally change small or large employer health benefit policy provisions except at renewal. However, issuers may modify the renewal date by obtaining the signed acceptance of the policyholder. If a change in the renewal date could impact the consumer’s out-of-pocket costs by resetting the deductible or out-of-pocket maximum, carriers are strongly encouraged to disclose this at the time of signed acceptance in order to avoid deceptive trade practice complaints.