Just tell them you would like for them to reconsider you for higher amount using the same HP they used to get you approved first time around. They will ask you again how much would you like, if you say too much they will counter offer their max. Good luck!
Congrats on the increase. Call them and say you really would like a higher limit so your utilization won't be too high when you use it. Ask for $20k and remind them you have a hp on file.
+1 Essential to remind them about your hp.