If the cardSelect variable is true, just let read select it
<select name="card-exp-month" #validateMonth formControlName="digiMes" class="form-
control" name="validade" id="validade" >
<option value="">Mês</option>
<option value="01">01 Jan</option>
<option value="02">02 Fev</option>
<option value="03">03 Mar</option>
<option value="04">04 Abr</option>
<option value="05">05 Mai</option>
<option value="06">06 Jun</option>
<option value="07">07 Jul</option>
<option value="08">08 Ago</option>
<option value="09">09 Set</option>
<option value="10">10 Out</option>
<option value="11">11 Nov</option>
<option value="12">12 Dez</option>
</select>
When is input text its works
<label for="nomeimpresso">Nome <b>impresso</b> no cartão<span class="text-danger"> *
</span></label>
<input #nomeImpresso formControlName="digiNome" name="holder-name" id="nomeimpresso"
class="form-control col-lg-6" type="text" [readonly]="cardSelect" >