9. A system, comprising: a memory to store a plurality of rules associated with performing speech recognition, at least a portion of the rules being based on constraints associated with a subject matter for which the speech recognition is to be performed; an input device to receive a telephone call from a caller; and at least one logic device to: determine a telephone number from which the telephone call was made, retrieve information based on the telephone number, receive a first voice input from the caller, generate a first speech recognition result corresponding to the first voice input, identify a first group of the plurality of rules based on the first speech recognition result, receive a second voice input, the second voice input including at least one of a plurality of characters in a sequence, generate a second speech recognition result based on the second voice input using a first group of rules stored in the memory, at least a first one of the first group of rules being associated with identifying one or more characters in the sequence and being constrained to identify one of a subset of characters based on a position in the sequence, the subset of characters including less than all of a possible number of characters, compare the retrieved information to the second speech recognition result; provide a first prompt to confirm the second speech recognition result; receive information indicating that the second speech recognition result does not correspond to the second voice input; apply, based on receiving the information indicating that the second speech recognition result does not correspond to the second voice input, a second group of the plurality of rules to the second voice input, the second group of the plurality of rules being different than the first group of the plurality of rules; generate a third speech recognition result based on applying the second group of rules to the second voice input; and provide a second prompt to confirm the third speech recognition result.
9. A system, comprising: a memory to store a plurality of rules associated with performing speech recognition, at least a portion of the rules being based on constraints associated with a subject matter for which the speech recognition is to be performed; an input device to receive a telephone call from a caller; and at least one logic device to: determine a telephone number from which the telephone call was made, retrieve information based on the telephone number, receive a first voice input from the caller, generate a first speech recognition result corresponding to the first voice input, identify a first group of the plurality of rules based on the first speech recognition result, receive a second voice input, the second voice input including at least one of a plurality of characters in a sequence, generate a second speech recognition result based on the second voice input using a first group of rules stored in the memory, at least a first one of the first group of rules being associated with identifying one or more characters in the sequence and being constrained to identify one of a subset of characters based on a position in the sequence, the subset of characters including less than all of a possible number of characters, compare the retrieved information to the second speech recognition result; provide a first prompt to confirm the second speech recognition result; receive information indicating that the second speech recognition result does not correspond to the second voice input; apply, based on receiving the information indicating that the second speech recognition result does not correspond to the second voice input, a second group of the plurality of rules to the second voice input, the second group of the plurality of rules being different than the first group of the plurality of rules; generate a third speech recognition result based on applying the second group of rules to the second voice input; and provide a second prompt to confirm the third speech recognition result. 13. The system of claim 9 , where the at least one logic device is further to: provide a first prompt to the caller; and receive the first voice input based on the first prompt, where, when generating the second speech recognition result the at least one logic device is to: use the first speech recognition result to select at least the first rule.