Select filled via ajax when selecting value from another select sending null to php

I have a select that populates another select via ajax, all values are filled correctly, however when saving, it sends null.

First select:

<select name="clientesel" class="form-control js-example-basic-multiple" id="clientesel" >
    <option value="">Selecione</option>                         
    <?php foreach ($clientes as $cliente) { ?>
    <option value="<?php echo $cliente['Cliente']['cli_codigo_id']; ?>"><?php echo $cliente['Cliente']['cli_codigo_id'] . " - " . $cliente['Pessoas']['pes_razao_nome']; ?></option>
    <?php } ?>
</select>

Second select

<select name="pagamento" class="form-control" id="pagamento">
    <option value="">Selecione</option>
    <?php foreach ($form_pagto as $pgto) { ?>
    <option value="<?php echo $pgto['FormaPagamento']['frec_codigo_id']; ?>"><?php echo $pgto['FormaPagamento']['frec_descricao']; ?></option>
    <?php } ?>
</select>

JS that fills the second from the first

$('#pagamento').val(data.Cliente.cli_forma_recebimento);
$("#pagamento option").each(function() {
    if($(this).val() == data.Cliente.cli_forma_recebimento) {
        $(this).attr("selected", true);
    }
});

HTML after running ajax

<select name="pagamento" class="form-control" id="pagamento" disabled="true">
    <option value="">Selecione</option>
    <option value="01" selected="selected">CHEQUE</option>
    <option value="02">BOLETO</option>
    <option value="03">DEPÓSITO</option>
    <option value="05">VALE</option>
    <option value="06">TRANSFERÊNCIA</option>
    <option value="07">SOMENTE DINHEIRO</option>
    <option value="08">SEM FATURA</option>
    <option value="09">CARTÃO DE DÉBITO</option>
    <option value="10">CARTÃO DE CRÉDITO</option>
</select>