Mango and LekkeVlieg pathetic communication

I’m not a regular flyer, big was my shock to find out with check in that the tickets I booked for me and my wife for a romantic trip to Durban are not next to each other. We had to sit in middle seats, spoiling my romantic getaway from the start. How can a airline allow random bookings to be made for a flight in advance, leaving all the middle seats open only to be allocated to suckers like me without giving me a choice to sit next to my wife? Last time flying Mango and booking through LekkeVlieg, you are a dissapointment!