After receiving the lawyer's letter from Telecom, you should check whether you have breached the contract or owed money according to the contents of the lawyer's letter. If so, you should get in touch with a lawyer in time and try to solve it through consultation, so as not to cause you extra and unnecessary economic losses.
If the lawyer's letter is not true, you can choose to ignore it or report the situation to the lawyer for verification by the telecom company.