No Service delivered

Tried to book seats on already booked flights. Went through the whole process up to confirmation of payment and then received a message 'sorry something went wrong. Tried again a few days later - same nonsense. Called the number given on the site as customer service. Went through the whole business of choosing options, listening to music after being advised the next agent will be with you shortly. Agent picked up receiver only to do nothing but terminate the call. Sent email to *** and *** only to receive messages that the emails could not be delivered as "550 Administrative prohibition - envelope blocked"