Thameslink and Great Northern has said sorry to rail passengers for further disruption to services after the introduction of a third new timetable in two months.
The operator offered an apology amid criticism which included one customer saying the service was “getting worse by the week”.
Hundreds of services have been cancelled since departure schedules were modified on May 20.
Thameslink and Great Northern introduced a third new timetable on Sunday.
The latest change will still see some services cancelled in advance, but rail bosses said they hoped the number of on-the-day cancellations will be reduced.
Meanwhile some passengers who enjoyed disruption-free journeys on Monday expressed cautious optimism.
An interim timetable was introduced on June 4 which saw around 6% of daily services removed, but reliability continued to struggle.
A passenger named Jude tweeted on Monday: “A predictable start to the @GNRailUK new interim timetable. More delays, cancellations, trains too full to get on and incorrect info on the app. Is this ever going to change? The service is getting worse by the week.”
In reply Great Northern tweeted: “Apologies for this. We are aware of a number of disruptions across our service today and we sincerely apologise to our customers. We don’t have a time-frame unfortunately.”
Great Northern apologised to another passenger who said she would be 45 minutes late to work after two fast trains into London were cancelled.
In response to a rail user who said passengers want trains running on time, rather than compensation for delays, Thameslink tweeted: “I understand and I apologise.”
Another traveller took exception when Great Northern said services were running well, instead describing them as an “an absolute disaster, with a sea of delays and cancellations”.
Elsewhere one passenger said getting a seat on an on-time train had happened for the first time since the initial timetable change in May.
Kate Dodsworth said she was “cautious yet jubilant”.
Another said they awaited their journey home on Monday evening “with great anticipation” after a smooth route into work.
Charles Horton, chief executive of Govia Thameslink Railway (GTR), parent company of Thameslink and Great Northern, announced his resignation in June.