communications company that does not know anything about communicating

a simple task like updating a contact number with the couriers is turning into a headache, ,im not sure whats the point of a Retentions department if all they do is say " we will escalate with courier and contact you back" but never do. i have been phoning in every day and have not been getting any assistance and now i get told the retentions department for a telecomunications company is unable to receive calls so they cant put me through.this is absolutely ridiculous