[drislerfottor]

As-Salamu `alaykum

Tawassul and Istighatha are different.

Istighatha is tawassul. Mufti Muhammad ibn Adam says in his answer (cited above):

This Tawassul may be expressed by using any phrase or done in any form, including:

Wasila (supplicating Allah through a means),

Istighatha (calling upon someone for help, through Allah’s love and concern for them),

Isti’ana (seeking someone’s assistance, through Allah’s granting). (Istighatha)
Istighatha is taught in the very hadith upon which the permissibility of tawassul is based; it is part of the sunna du`a of tawassul that the Prophet (Allah bless him and give him peace) taught the blind man.