No, Bassanio betrays Portia's trust when he sends his ring to the "lawyer" who defended Antonio and saved him from giving up a pound of flesh to Shylock.
After his merchant ships were lost at sea and he can't repay the three thousand ducats Shylock loaned him, Antonio is called before the Duke of Venice.
Shylock demands the forfeiture of a pound of flesh from the Antonio, and the Duke sees no way to prevent Shylock's collection on the unpaid loan. Fortuitously, a doctor of law, Portia in disguise, enters and raises the point that the contract does not include Antonio's blood. Therefore, Shylock may only have a pound of flesh if there is no bleeding when the flesh is cut. Since this is impossible, the doctor of law saves Antonio.
When Antonio offers to requite the lawyer's efforts in saving him, Portia replies, "He is well paid that is well satisfied" (4.1.415). However, Bassanio insists that the lawyer take something, so Portia asks for his gloves, which he freely gives. Then, the lawyer asks for Bassanio's ring. Bassanio refuses, saying that there is more that depends upon this ring than its value and offers to give something else.
When Portia insists, Antonio persuades Bassanio to part with the ring. Because Antonio has endured so much for Bassanio's sake, Bassanio sends the ring to the doctor of law.
While Bassanio does betray his promise to Portia, he reinforces the importance of male friendships in Elizabethan times as his indebtedness to Anotonio for the opportunity to marry Portia overrides his promise to his wife to wear a ring.