Contact TD Ameritrade by telephone on 800 669 3900. This is their customer service number and is only for existing customers. If you are looking to set up a new account then use the number 800 454 9272.
Be aware that this is a US number so you may have to use the international dialling code +1 if dialling from outside the country.
Skype Phone TD Ameritrade
Be aware, also, that international calls can incur hefty charges, therefore you should try to use Skype where possible. If you have a Microsoft 365 account then you will have a certain amount of free Skype minutes per month. If not you can by a Skype subscription to make your call.