It this sentence, the 'Ir+a+infinitive' structure is being used. It is just in the past tense (preterite). For 'I was using the phone.', you could use the imperfect tense, '(Yo) utilizaba el teléfono.', which is probably the most common way, but you can also use 'Estar+gerundio', using both the preterite and imperfect for estar. '(Yo) estuve utilizando...' and '(Yo) estaba utilizando...', although these forms are less common, but correct. Ser doesn't work in any of these cases. The problem is Ir and Ser conjugate the same in the preterite tense, and if you aren't familiar with that, it can be confusing. Hope that helps.
Thanks pobrecito! I just want to tell others that I know when I was learning this phrase I had not been exposed to using the imperfect tense so when you see this response don't concern yourself with imperfect until you hit that module. When I asked the question I didnt know it would trigger the imperfect. It all comes together later.
The preterit for the verb "ir" (to go) and the verb "ser"(to be) are the same(fui). http://www.spanishdict.com/translate/ir#conjugation http://www.spanishdict.com/translate/ser#conjugation I'm not sure what forces it to be the verb "ir" here though. Could be the "a" it often used for movements.
I said "I was going to use the phone" but was marked wrong. In present tense, "I am going to use the phone" would be "voy a usar el teléfono". Am not sure why cannot use "fui a usar" for "was going to use" iff "voy a usar" can mean "am going to use". Can anyone explain? Thanks!
Could someone please answer wynrich's question above? I understand all the other responses to date, but none seem to answer that question. If "ir+a+inf." means "am/is/are going to + inf." then why couldn't the sentence here mean "was going to use the telephone"? Pobrecito addresses the imperfect for "I was using..." but not for "I was going to use...". So, would Spanish speakers only use the imperfect of "ir" in this case? As in "Iba a utilizar..." for "was going to use"? Seems to me I've seen the preterit of "ir" used for "was going to". Thanks!!
Imagine the Dark Ages, before cell phones. Employees aren't allowed to use the office phone for personal calls. Smith has to leave the office to make his call. He goes into the hall to use an anachronism known as a public phone. When he returns, his boss booms, "Smith! Where were you?" "I went to use the phone."