Downgraded from 10mbps to 4mbps after line fix

My ADSL line went dead on Monday 19 October, so when I arrived at home I noticed and called 10210, Option 2, Option 2, Entered my number, Option 3. I spoke to a person who logged the fault after which I received an SMS confirming the fault. After 3 days of phoning once a day, and escalating the ticket, the line was fixed. BUT, it was downgraded to 4mbps whereas I had a stable 10mbps line up until Monday 11:15am. Been living in my house for a year now with no issues. Why was I downgraded and for what reason? My ADSL stats are all good, so they cannot tell me I'm too far from the exchange or the copper is degraded. Copper doesn't degrade in 1 day. I think my slot at the exchange has been swapped with someone else and they think I will not notice. Please contact me so we can sort this out.