I was taught at dog training to teach recall on lead until sure the dog obeyed the command without hesitating.
Maybe you could use the long line to help teach the 'come' voice command and also as a precaution for stepping on if needed but how about trying a dog whistle. Whistle = treat.
Sometimes we can have different tones in our voices without realising it, if we are in a bad mood or frustrated etc. A whistle takes this out of the equasion. Works most of the time with all my dogs and even if I haven't used the whistle in ages they still come back if I use it.
We also tend to tell our dogs off when they eventually do come back and this just associates coming back with a telling off. Best to ignore them if they run off and then decide to come back after they have ignored you.
If all else fails 'run backwards in the opposite direction of your dog calling come in a silly voice with your arms spread outwards' (same as the aeroplane theory and yes you will look a twit but if it works then hey?? if you chase after a dog it will run away if you run away it will chase you that is of course unless like on of mine is focused on a rabbit in that case and then Ive got no chance lol