In previous games, to get rematches with trainers, you used the VS Seeker to see if the trainers were willing to battle. In HeartGold & SoulSilver however, the rematches are done a different way. Firstly, only a few dozen trainers in Kanto & Johto are capable of being battled again.

In order to get the rematch, you have to receive the PokéGear number from the trainer in question. Then, on a certain day, you will need to ring the trainer in question to organise a rematch. It is not guaranteed that a rematch will be discussed when you call but keep trying and you should get it. Below is a list of all the trainers, battleable on Friday, and their teams including their first team and each team's increase in level. Click the other days to go to their page

Monday | Tuesday | Wednesday | Thursday | Friday | Saturday | Sunday

Friday

Time	Location	Trainer
Morning 4am-10am	Johto - Route 38	School Kid Chad
Teams First Battle School Kid Chad Mr. Mime Level 20 Second Battle School Kid Chad Mr. Mime Magnemite Level 29 Level 30 Third Battle School Kid Chad Mr. Mime Magneton Level 39 Level 38 Fourth Battle School Kid Chad Mr. Mime Magneton Level 46 Level 56
Morning 4am-10am	Kanto - Route 2	Bug Catcher Rob
Teams First Battle Bug Catcher Rob Beedrill Butterfree Level 40 Level 39 Second Battle Bug Catcher Rob Beedrill Butterfree Level 45 Level 42 Third Battle Bug Catcher Rob Beedrill Butterfree Level 52 Level 48 Fourth Battle Bug Catcher Rob Beedrill Butterfree Level 56 Level 56
Day 10am-8pm	Johto - Route 45	Hiker Parry
Teams First Battle Hiker Parry Onix Level 30 Second Battle Hiker Parry Onix Graveler Level 38 Level 35 Third Battle Hiker Parry Steelix Graveler Level 41 Level 37 Fourth Battle Hiker Parry Steelix Golem Level 56 Level 52
Day 10am-8pm	Kanto - Route 13	Young Couple Tim & Sue
Teams First Battle Young Couple Tim & Sue Kadabra Psyduck Level 41 Level 46 Second Battle Young Couple Tim & Sue Kadabra Golduck Level 45 Level 50 Third Battle Young Couple Tim & Sue Kadabra Golduck Level 48 Level 52 Fourth Battle Young Couple Tim & Sue Alakazam Golduck Level 54 Level 56
Day 10am-8pm	Kanto - Route 26	Ace Trainer Jamie
Teams First Battle Ace Trainer Jamie Rapidash Flaaffy Level 36 Level 31 Second Battle Ace Trainer Jamie Rapidash Ampharos Level 38 Level 37 Third Battle Ace Trainer Jamie Rapidash Ampharos Level 42 Level 40 Fourth Battle Ace Trainer Jamie Rapidash Ampharos Level 56 Level 59
Night 8pm-5am	Johto - Route 33	Hiker Anthony
Teams First Battle Hiker Anthony Geodude Machop Level 11 Level 11 Second Battle Hiker Anthony Graveler Machoke Level 33 Level 32 Third Battle Hiker Anthony Graveler Graveler Machoke Level 37 Level 38 Level 40 Fourth Battle Hiker Anthony Graveler Golem Machamp Level 41 Level 49 Level 55
Night 8pm-5am	Kanto - Route 15	School Kid Billy
Teams First Battle School Kid Billy Parasect Poliwhirl Ditto Level 39 Level 37 Level 35 Second Battle School Kid Billy Parasect Poliwhirl Ditto Level 42 Level 43 Level 40 Third Battle School Kid Billy Parasect Poliwhirl Ditto Level 46 Level 47 Level 46 Fourth Battle School Kid Billy Mr. Mime Parasect Poliwrath Ditto Level 50 Level 55 Level 53 Level 51